feat: multiple playground choices (#5207)

* poc of using netlify functions for playground redirections

* push

* cleanup

* restore files

* fix netlify functions?

* fix netlify functions?

* implement serverless functions for playgrounds with persistent cookie

* move new.docusaurus.io to monorepo packages

* move new.docusaurus.io to monorepo packages

* lockfile

* push

* catch-all redirect

* Translate/Interpolate: add better error message if not used correctly

* Add /docs/playground page

* Add some additional doc

website/versioned_docs/version-2.0.0-beta.3/playground.mdx

@@ -0,0 +1,24 @@
+# Playground
+
+Playgrounds allow you to run Docusaurus **in your browser, without installing anything**!
+
+They are mostly useful for:
+
+- Testing Docusaurus
+- Reporting bugs
+
+Use [new.docusaurus.io](https://new.docusaurus.io) as an easy-to-remember shortcut.
+
+Choose one of the available options below.
+
+```mdx-code-block
+import {PlaygroundCardsRow} from '@site/src/components/Playground';
+
+<PlaygroundCardsRow />
+```
+
+:::tip
+
+For convenience, we'll remember your choice next time you visit [new.docusaurus.io](https://new.docusaurus.io).
+
+:::