fix(elisp): add lexical-binding comment to all files to suppress new Emacs 31 warnings

I've set `lexical-binding` to `nil` in all Emacs Lisp files to suppress
the warnings introduced in Emacs 31 requiring all elisp files to have a
`lexical-binding` comment.

This retains the default behavior of dynamic binding when no
`lexical-binding` comment is present. With it set to `t` across the
board, various things break, and fixing those is a task for another day.

modules/navigation/siren-anzu.el

@@ -1,4 +1,4 @@
-;;; siren-anzu.el --- jimeh's Emacs Siren: anzu configuration.
+;;; siren-anzu.el --- jimeh's Emacs Siren: anzu configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/navigation/siren-avy.el

@@ -1,4 +1,4 @@
-;;; siren-avy.el --- jimeh's Emacs Siren: avy configuration.
+;;; siren-avy.el --- jimeh's Emacs Siren: avy configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/navigation/siren-better-jumper.el

@@ -1,4 +1,4 @@
-;;; siren-better-jumper.el --- jimeh's Emacs Siren: better-jumper configuration.
+;;; siren-better-jumper.el --- jimeh's Emacs Siren: better-jumper configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/navigation/siren-centaur-tabs.el

@@ -1,4 +1,4 @@
-;;; siren-centaur-tabs.el --- jimeh's Emacs Siren: centaur-tabs configuration.
+;;; siren-centaur-tabs.el --- jimeh's Emacs Siren: centaur-tabs configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/navigation/siren-consult.el

@@ -1,4 +1,4 @@
-;;; siren-consult.el --- jimeh's Emacs Siren: consult configuration.
+;;; siren-consult.el --- jimeh's Emacs Siren: consult configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/navigation/siren-ctrlf.el

@@ -1,4 +1,4 @@
-;;; siren-ctrlf.el --- jimeh's Emacs Siren: ctrlf configuration.
+;;; siren-ctrlf.el --- jimeh's Emacs Siren: ctrlf configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/navigation/siren-dired+.el

@@ -1,4 +1,4 @@
-;;; siren-dired+.el --- jimeh's Emacs Siren: dired+ configuration.
+;;; siren-dired+.el --- jimeh's Emacs Siren: dired+ configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/navigation/siren-dired.el

@@ -1,4 +1,4 @@
-;;; siren-dired.el --- jimeh's Emacs Siren: dired configuration.
+;;; siren-dired.el --- jimeh's Emacs Siren: dired configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/navigation/siren-direx.el

@@ -1,4 +1,4 @@
-;;; siren-direx.el --- jimeh's Emacs Siren: direx configuration.
+;;; siren-direx.el --- jimeh's Emacs Siren: direx configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/navigation/siren-dirvish.el

@@ -1,4 +1,4 @@
-;;; siren-dirvish.el --- jimeh's Emacs Siren: dirvish configuration.
+;;; siren-dirvish.el --- jimeh's Emacs Siren: dirvish configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/navigation/siren-dumb-jump.el

@@ -1,4 +1,4 @@
-;;; siren-dumb-jump.el --- jimeh's Emacs Siren: dumb-jump configuration.
+;;; siren-dumb-jump.el --- jimeh's Emacs Siren: dumb-jump configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/navigation/siren-full-ack.el

@@ -1,4 +1,4 @@
-;;; siren-full-ack.el --- jimeh's Emacs Siren: full-ack configuration.
+;;; siren-full-ack.el --- jimeh's Emacs Siren: full-ack configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/navigation/siren-git-link.el

@@ -1,4 +1,4 @@
-;;; siren-git-link.el --- jimeh's Emacs Siren: git-link configuration.
+;;; siren-git-link.el --- jimeh's Emacs Siren: git-link configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/navigation/siren-goto-symbol.el

@@ -1,4 +1,4 @@
-;;; siren-goto-symbol.el --- jimeh's Emacs Siren: goto-symbol.
+;;; siren-goto-symbol.el --- jimeh's Emacs Siren: goto-symbol.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/navigation/siren-helm-ag.el

@@ -1,4 +1,4 @@
-;;; siren-helm-ag.el --- jimeh's Emacs Siren: helm-ag configuration.
+;;; siren-helm-ag.el --- jimeh's Emacs Siren: helm-ag configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/navigation/siren-helm-gtags.el

@@ -1,4 +1,4 @@
-;;; siren-helm-gtags.el --- jimeh's Emacs Siren: helm-gtags configuration.
+;;; siren-helm-gtags.el --- jimeh's Emacs Siren: helm-gtags configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/navigation/siren-helm-open-github.el

@@ -1,4 +1,4 @@
-;;; siren-helm-open-github.el --- jimeh's Emacs Siren: helm-open-github configuration.
+;;; siren-helm-open-github.el --- jimeh's Emacs Siren: helm-open-github configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/navigation/siren-helm-swoop.el

@@ -1,4 +1,4 @@
-;;; siren-helm-swoop.el --- jimeh's Emacs Siren: helm-swoop configuration.
+;;; siren-helm-swoop.el --- jimeh's Emacs Siren: helm-swoop configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/navigation/siren-helm.el

@@ -1,4 +1,4 @@
-;;; siren-helm.el --- jimeh's Emacs Siren: helm configuration.
+;;; siren-helm.el --- jimeh's Emacs Siren: helm configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/navigation/siren-imenu.el

@@ -1,4 +1,4 @@
-;;; siren-imenu.el --- jimeh's Emacs Siren: imenu configuration.
+;;; siren-imenu.el --- jimeh's Emacs Siren: imenu configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/navigation/siren-isearch.el

@@ -1,4 +1,4 @@
-;;; siren-isearch.el --- jimeh's Emacs Siren: isearch configuration.
+;;; siren-isearch.el --- jimeh's Emacs Siren: isearch configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/navigation/siren-move-beginning-of-line.el

@@ -1,4 +1,4 @@
-;;; siren-move-beginning-of-line.el --- jimeh's Emacs Siren: move-beginning-of-line.
+;;; siren-move-beginning-of-line.el --- jimeh's Emacs Siren: move-beginning-of-line.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/navigation/siren-recursive-narrow.el

@@ -1,4 +1,4 @@
-;;; siren-recursive-narrow.el --- jimeh's Emacs Siren: recursive-narrow configuration.
+;;; siren-recursive-narrow.el --- jimeh's Emacs Siren: recursive-narrow configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/navigation/siren-scroll-half-screen.el

@@ -1,4 +1,4 @@
-;;; siren-scroll-half-screen.el --- jimeh's Emacs Siren: scroll-half-screen.
+;;; siren-scroll-half-screen.el --- jimeh's Emacs Siren: scroll-half-screen.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/navigation/siren-swiper.el

@@ -1,4 +1,4 @@
-;;; siren-swiper.el --- jimeh's Emacs Siren: swiper configuration.
+;;; siren-swiper.el --- jimeh's Emacs Siren: swiper configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary: