feat(lang): Language aware syntax highlight of markdown code-blocks

Enable polymode within code-blocks in Markdown files. Effectively, it
allows code-blocks of various languages to be handled by their
respective major modes, allowing correct syntax highlighting, snippets,
and other features to work as you would expect.

modules/languages/siren-markdown.el

@@ -10,6 +10,7 @@
 (require 'siren-display-line-numbers)
 (require 'siren-flyspell)
 (require 'siren-move-dup)
+(require 'siren-polymode)
 (require 'siren-prettier-js)
 (require 'siren-smartparens)
 
@@ -54,5 +55,13 @@
 (use-package edit-indirect
   :defer t)
 
+(use-package poly-markdown
+  :mode
+  ("\\.md" . poly-markdown-mode)
+  ("\\.mkd" . poly-markdown-mode)
+  ("\\.mkdn" . poly-markdown-mode)
+  ("\\.mdown" . poly-markdown-mode)
+  ("\\.markdown" . poly-markdown-mode))
+
 (provide 'siren-markdown)
 ;;; siren-markdown.el ends here

modules/languages/siren-polymode.el

@@ -0,0 +1,13 @@
+;;; siren-polymode.el --- jimeh's Emacs Siren: polymode configuration.
+
+;;; Commentary:
+
+;; Basic configuration for polymode.
+
+;;; Code:
+
+(use-package polymode
+  :defer t)
+
+(provide 'siren-polymode)
+;;; siren-polymode.el ends here