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/org-mode/siren-htmlize.el

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

modules/org-mode/siren-ob-go.el

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

modules/org-mode/siren-ob-http.el

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

modules/org-mode/siren-ob-mermaid.el

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

modules/org-mode/siren-org-mode.el

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

modules/org-mode/siren-ox-gfm.el

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

modules/org-mode/siren-ox-jira.el

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

modules/org-mode/siren-ox-pandoc.el

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