feat(v2): docs options.onlyIncludeVersions (#3373)

* docs options.onlyIncludeVersions

* adapt docsVersionDropdown if we render a single version

* fix bad error message

* fix netlify deploy when versioning is disabled

website/docs/using-plugins.md

@@ -362,6 +362,11 @@ module.exports = {
           },
           */
         },
+        /**
+         * Sometimes you only want to include a subset of all available versions.
+         * Tip: limit to 2 or 3 versions to improve startup and build time in dev and deploy previews
+         */
+        onlyIncludeVersions: undefined, // ex: ["current", "1.0.0", "2.0.0"]
       },
     ],
   ],

website/docusaurus.config.js

@@ -178,6 +178,10 @@ module.exports = {
           remarkPlugins: [require('./src/plugins/remark-npm2yarn')],
           disableVersioning: isVersioningDisabled,
           lastVersion: isDev || isDeployPreview ? 'current' : undefined,
+          onlyIncludeVersions:
+            !isVersioningDisabled && (isDev || isDeployPreview)
+              ? ['current', ...versions.slice(0, 2)]
+              : undefined,
           versions: {
             current: {
               // path: isDev || isDeployPreview ? '' : 'next',