If you don't want to copy-paste this all over your different repositories, you can also try this NPM package or this Bit component.
They should work just fine and make it useable anywhere you need.
AltStyle によって変換されたページ (->オリジナル) / アドレス: モード: デフォルト 音声ブラウザ ルビ付き 配色反転 文字拡大 モバイル
If you don't want to copy-paste this all over your different repositories, you can also try this NPM package or this Bit component.
They should work just fine and make it useable anywhere you need.