Add outdated component to outdated documents (#25)

- `git log` needs all commit history to compare latest commit of files, so changed `git clone --depth=1` to `git clone`. This will make the step take longer, so might be improved if there is a better way.

- `src/theme/MDXContent/index.js` is from [ejecting of the component](https://docusaurus.io/docs/swizzling#ejecting) inside `@docusaurus/theme-classic` plugin, and this one is safe to eject according to docusaurus

    ![Screen Shot 2023-06-06 at 12.12.28](/attachments/17a3a84b-cec0-4849-8bd6-9e0471d9536f)

    ![Screen Shot 2023-06-06 at 12.12.15](/attachments/58bba321-3cfb-4a8b-8aeb-84422a06c472)

- [Outdated component style reference](https://mui.com/material-ui/react-alert/)

- Added [`Translate` component](https://docusaurus.io/docs/next/docusaurus-core#translate) to `Outdated` so it can be localized. [reference](https://docusaurus.io/docs/next/i18n/tutorial#translate-your-react-code)

- One way to check for the specific outdated documents:

    search for `lastest commit timestamp` in [prepare nightly docs and prepare 1.19 docs steps](https://gitea.com/gitea/gitea-docusaurus/actions/runs/74)

# After

The Chinese documents that are outdated (latest commit is ealier than laster commit of English version):

![Screen Shot 2023-06-06 at 13.04.24](/attachments/e5d16267-d8d8-434e-89b1-138d04ec92a3)

![Screen Shot 2023-06-06 at 13.05.07](/attachments/af8f996a-5318-4f89-841f-b27a4903a27d)

![Screen Shot 2023-06-06 at 13.05.14](/attachments/e6aba31b-46ba-4a32-ad81-81007e0f711e)

Reviewed-on: https://gitea.com/gitea/gitea-docusaurus/pulls/25
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: HesterG <hestergong@gmail.com>
Co-committed-by: HesterG <hestergong@gmail.com>

docusaurus.config.js

@@ -24,12 +24,11 @@ const config = {
   favicon: 'img/favicon.png',
 
   i18n: {
-    defaultLocale: 'en',
-    locales: ['en', 'zh-cn'/*, 'fr-fr', 'zh-tw'*/], // temporarily disable other locales
+    defaultLocale: 'en-us',
+    locales: ['en-us', 'zh-cn'/*, 'fr-fr', 'zh-tw'*/], // temporarily disable other locales
     localeConfigs: {
-      'en': {
+      'en-us': {
         label: 'English',
-        htmlLang: 'en-US',
       },
       'zh-cn': {
         label: '中文',
@@ -47,15 +46,12 @@ const config = {
           sidebarPath: require.resolve('./sidebars.js'),
           routeBasePath: '/', // Serve the docs at the site's root
           editUrl: ({versionDocsDirPath, docPath, locale, version, permalink}) => {
-            let fileName = `doc/${docPath.replace('.md', '')}.en-us.md`;
-            if (locale === 'zh-cn') {
-              fileName = `doc/${docPath.replace('.md', '')}.zh-cn.md`;
-            }
+            let fileName = `doc/${docPath.replace('.md', '')}.${locale}.md`;
             // intro.md has different name from upstream, need to handle this here
             if (docPath.includes('intro.md')) {
-              fileName = locale === 'zh-cn' ? 'page/index.zh-cn.md': 'page/index.en-us.md';
+              fileName = `page/index.${locale}.md`;
             }
-            return `https://github.com/go-gitea/gitea/tree/main/docs/content/${fileName}`;
+            return `https://github.com/go-gitea/gitea/tree/${version === 'current' ? 'main': `release/v${version}`}/docs/content/${fileName}`;
           },
           versions: {
             current: {