chore: Reference Github code in Docusaurus (#18229)

* POC github code reference

* Add example

* Remove unnecessary change

* Remove POC page

docs-v2/docusaurus.config.js

@@ -35,6 +35,9 @@ const config = {
   favicon: 'img/favicon.ico',
   organizationName: 'apache', // Usually your GitHub org/user name.
   projectName: 'superset', // Usually your repo name.
+    themes: [
+        '@saucelabs/theme-github-codeblock'
+    ],
    plugins: [
     [
       '@docusaurus/plugin-client-redirects',