docs: allow for toggling light/dark mode (#2869)

mkdocs.yml

@@ -15,6 +15,27 @@ theme:
     - navigation.top
     - navigation.indexes
   locale: en
+  palette:
+
+    # Palette toggle for automatic mode
+    - media: "(prefers-color-scheme)"
+      toggle:
+        icon: material/brightness-auto
+        name: Switch to light mode
+
+    # Palette toggle for light mode
+    - media: "(prefers-color-scheme: light)"
+      scheme: default
+      toggle:
+        icon: material/brightness-7
+        name: Switch to dark mode
+
+    # Palette toggle for dark mode
+    - media: "(prefers-color-scheme: dark)"
+      scheme: slate
+      toggle:
+        icon: material/brightness-4
+        name: Switch to system preference
 
   highlightjs: true
   hljs_languages: