refactor: 独自要素のスタイルを管理するCSSのファイル名をcustom.cssに変更

Author: 3w36zj6

static/styles/docs-cn.css renamed to static/styles/custom.css

@@ -27,7 +27,7 @@
   <link rel="manifest" href="/assets/site.webmanifest">
   <link rel="stylesheet" href="/styles/default.css?bust=20230913?d=2023-09-16">
   <link rel="stylesheet" href="/styles/docs.css?bust=20230915?d=2023-09-16">
-  <link rel="stylesheet" href="/styles/docs-cn.css">
+  <link rel="stylesheet" href="/styles/custom.css">
   <link rel="preload" href="/assets/fonts/HKGrotesk-Regular.woff2" as="font">
   <link rel="preload" href="/assets/fonts/HKGrotesk-Bold.woff2" as="font">
   <link rel="preload" href="/assets/fonts/HKGrotesk-SemiBold.woff2" as="font">