feat(shortcodes): add .md templates for icon aliases

Icon shortcodes (icon, fa, fab, far, fas) are decorative and
carry no textual meaning for LLM consumers. Add empty .md
markdown output templates so Hugo uses them instead of the
HTML templates when rendering the markdown output format,
suppressing safe-content HTML warnings.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: markdumay

layouts/_shortcodes/fa.md

@@ -0,0 +1,5 @@
+{{- /*
+  Markdown output template for the fa shortcode alias.
+  Icons are decorative and carry no textual meaning for LLM consumers,
+  so this template intentionally produces no output.
+*/ -}}

layouts/_shortcodes/fab.md

@@ -0,0 +1,5 @@
+{{- /*
+  Markdown output template for the fab shortcode alias.
+  Icons are decorative and carry no textual meaning for LLM consumers,
+  so this template intentionally produces no output.
+*/ -}}

layouts/_shortcodes/far.md

@@ -0,0 +1,5 @@
+{{- /*
+  Markdown output template for the far shortcode alias.
+  Icons are decorative and carry no textual meaning for LLM consumers,
+  so this template intentionally produces no output.
+*/ -}}

layouts/_shortcodes/fas.md

@@ -0,0 +1,5 @@
+{{- /*
+  Markdown output template for the fas shortcode alias.
+  Icons are decorative and carry no textual meaning for LLM consumers,
+  so this template intentionally produces no output.
+*/ -}}

layouts/_shortcodes/icon.md

@@ -0,0 +1,5 @@
+{{- /*
+  Markdown output template for the icon shortcode.
+  Icons are decorative and carry no textual meaning for LLM consumers,
+  so this template intentionally produces no output.
+*/ -}}