chore(lang): Add support for mermaid diagrams

The org-babal features of mermaid-mode itself don't seem to work, but
the separate ob-mermaid does work.

core/siren-core-modules.el

@@ -113,6 +113,7 @@
 ;; Org-mode
 (require 'siren-htmlize)
 (require 'siren-org-mode)
+(require 'siren-ob-mermaid)
 (require 'siren-ox-gfm)
 (require 'siren-ox-jira)
 
@@ -140,6 +141,7 @@
 (require 'siren-lua)
 (require 'siren-makefile)
 (require 'siren-markdown)
+(require 'siren-mermaid)
 (require 'siren-php)
 (require 'siren-plantuml)
 (require 'siren-ruby)

modules/languages/siren-mermaid.el

@@ -0,0 +1,22 @@
+;;; siren-mermaid.el --- jimeh's Emacs Siren: mermaid-mode configuration.
+
+;;; Commentary:
+
+;; Basic configuration for mermaid-mode.
+
+;;; Code:
+
+(require 'siren-prog-mode)
+
+(use-package mermaid-mode
+  :mode "\\.mermaid\\'" "\\.mmd\\'"
+
+  :hook
+  (mermaid-mode . siren-mermaid-mode-setup)
+
+  :init
+  (defun siren-mermaid-mode-setup ()
+    (run-hooks 'prog-mode-hook)))
+
+(provide 'siren-mermaid)
+;;; siren-mermaid.el ends here

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

@@ -0,0 +1,22 @@
+;;; siren-ob-mermaid.el --- jimeh's Emacs Siren: ob-mermaid configuration.
+
+;;; Commentary:
+
+;; Basic configuration for ob-mermaid.
+
+;;; Code:
+
+(require 'siren-org-mode)
+
+(use-package ob-mermaid
+  :defer t
+
+  :hook
+  (org-mode . siren-ob-mermaid-setup)
+
+  :init
+  (defun siren-ob-mermaid-setup ()
+    (require 'ob-mermaid)))
+
+(provide 'siren-ob-mermaid)
+;;; siren-ob-mermaid.el ends here