Use custom api dropdown and fix compatibility for firefox (#39)

- Used custom api dropdown for changing label dynamically. Used method discussed in [this post](https://github.com/facebook/docusaurus/pull/7231). `ComponentTypes` is ejected safely.

  ![Screen Shot 2023-07-05 at 16.21.43](/attachments/b4bc8ae4-6a8a-406c-98b7-f739b13c32ba)

- Fixed dropdowns missing on chrome docs page

  ![Screen Shot 2023-07-05 at 16.44.08](/attachments/1e5315b4-a057-4325-990f-1cbc35fb475f)

-  Fixed `:has` selector compatibility problem on firefox. After (Screenshots from firefox):

  ![Screen Shot 2023-07-05 at 16.10.23](/attachments/76475fb6-fd58-42ec-b4be-6a774553a887)

  ![Screen Shot 2023-07-05 at 16.10.35](/attachments/956f623a-afdb-4ab4-8aa2-beb9420727fb)

  ![Screen Shot 2023-07-05 at 16.15.35](/attachments/af840f31-def4-4f72-8340-f29b72a748bd)

  ![Screen Shot 2023-07-05 at 16.09.30](/attachments/42fa2394-962d-4594-8ef3-c594d3c1e777)

Reviewed-on: https://gitea.com/gitea/gitea-docusaurus/pulls/39
Co-authored-by: HesterG <hestergong@gmail.com>
Co-committed-by: HesterG <hestergong@gmail.com>

docusaurus.config.js

@@ -13,13 +13,13 @@ function sortItemsByCategory(items) {
   return sortedItems;
 }
 
-const includeAPI = process.env.INCLUDE_API !== 'false';
+const renderApiSSR = process.env.API_SSR !== 'false';
 
 const apiConfig = [
   'redocusaurus',
   {
     // Plugin Options for loading OpenAPI files
-    specs: includeAPI ? [
+    specs: renderApiSSR ? [
       {
         spec: 'static/swagger-latest.json',
         route: '/api/next/',
@@ -41,7 +41,7 @@ const apiConfig = [
   },
 ]
 
-const pageConfig = includeAPI ? {
+const pageConfig = renderApiSSR ? {
   exclude: [
     'api/**',
   ],
@@ -167,15 +167,14 @@ const config = {
             activeBaseRegex: 'api/(1.19|1.20|next)/',
           },
           {
-            type: 'dropdown',
+            type: 'custom-apiDropdown',
             label: 'API Version',
             position: 'right',
             items: [
               {to: '/api/next/', label: '1.21-dev' },
-              {to: '/api/1.20/', label: '1.20.0-rc0' },
+              {to: '/api/1.20/', label: '1.20.0-rc2' },
               {to: '/api/1.19/', label: '1.19.4' },
             ],
-            className: 'api-dropdown',
           },
           {
             href: 'https://github.com/go-gitea/gitea',