docs: improve user guide search

Author: Djaytan

docs/user-guide/mkdocs.yml

@@ -19,6 +19,8 @@ theme:
     - navigation.instant.progress
     - navigation.sections
     - navigation.top
+    - search.suggest
+    - search.highlight
 
   palette:
     # Palette toggle for automatic mode
@@ -52,6 +54,9 @@ nav:
       - Configuration Files: configuration-files.md
   - License: license.md
 
+plugins:
+  - search
+
 markdown_extensions:
   - admonition