Docs automatic light/dark mode (#6287)

Signed-off-by: Glenn Jocher <glenn.jocher@ultralytics.com>
Co-authored-by: Sergiu Waxmann <47978446+sergiuwaxmann@users.noreply.github.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

docs/mkdocs_ja.yml

@@ -23,16 +23,24 @@ theme:
   #  text: Helvetica
   #  code: Roboto Mono
   palette:
-    - scheme: default  # light mode
-      # primary: grey
+    - media: "(prefers-color-scheme)"
       toggle:
-        icon: material/toggle-switch
-        name: Switch to dark mode
-    - scheme: slate  # dark mode
-      # primary: black
-      toggle:
-        icon: material/toggle-switch-off-outline
+        icon: material/brightness-auto
         name: Switch to light mode
+    - media: "(prefers-color-scheme: dark)"
+      scheme: slate
+      primary: black
+      accent: indigo
+      toggle:
+        icon: material/brightness-4
+        name: Switch to system preference
+    - media: "(prefers-color-scheme: light)"
+      scheme: default
+      primary: indigo
+      accent: indigo
+      toggle:
+        icon: material/brightness-7
+        name: Switch to dark mode
   features:
     - announce.dismiss
     - content.action.edit
@@ -110,6 +118,8 @@ extra:
 
 extra_css:
   - 'stylesheets/style.css'
+extra_javascript:
+  - 'javascript/extra.js'
 
 markdown_extensions:
   - admonition