docs: cross-link to gemmology.dev interactive surfaces

docs/index.md

@@ -2,7 +2,10 @@
 
 **Crystal Description Language (CDL) Parser** - A Python library for parsing compact string notation describing crystal morphology for gemmological and mineralogical visualization.
 
-Part of the [Gemmology Project](https://gemmology.dev).
+!!! tip "Interactive companion"
+    See live examples in the [CDL Playground](https://gemmology.dev/playground/),
+    browse 96+ rendered presets in the [Crystal Gallery](https://gemmology.dev/gallery/),
+    or take a [practice quiz](https://gemmology.dev/quiz/) on related material.
 
 ## Overview
 

mkdocs.yml

@@ -47,6 +47,7 @@ nav:
   - API Reference: api.md
   - CLI Usage: cli.md
   - Examples: examples.md
+  - "Try interactive ↗": https://gemmology.dev/playground/
 
 markdown_extensions:
   - pymdownx.highlight:
@@ -62,8 +63,20 @@ markdown_extensions:
   - tables
 
 extra:
+  generator: false
   social:
     - icon: fontawesome/brands/github
       link: https://github.com/gemmology-dev
-    - icon: fontawesome/solid/globe
-      link: https://gemmology.dev
+      name: GitHub
+    - icon: fontawesome/solid/flask
+      link: https://gemmology.dev/playground/
+      name: CDL Playground
+    - icon: fontawesome/solid/graduation-cap
+      link: https://gemmology.dev/quiz/
+      name: Practice quiz
+    - icon: fontawesome/solid/gem
+      link: https://gemmology.dev/gallery/
+      name: Crystal gallery
+    - icon: fontawesome/solid/book
+      link: https://gemmology.dev/learn/
+      name: Learn (FGA)