fix: add pymdownx.emoji extension for Material icon rendering

The :material-open-in-new: icon syntax in buttons requires the
pymdownx.emoji markdown extension to render as SVG icons.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: yepzdk

mkdocs.yml

@@ -51,6 +51,9 @@ markdown_extensions:
   - tables
   - attr_list
   - md_in_html
+  - pymdownx.emoji:
+      emoji_index: !!python/name:material.extensions.emoji.twemoji
+      emoji_generator: !!python/name:material.extensions.emoji.to_svg
   - toc:
       permalink: true