Replace Playground with JSX Editor (#1500)

Summary:
Pull Request resolved: https://github.com/facebook/yoga/pull/1500

Inspired by the frequent usage of Expo snacks to run RN, to repro Yoga issues, this replaces the Playground port with a new ground up Playground UI. This UI right now is pretty simple, with a JSX editor which creates a Yoga tree, which is then rendered using the WebAssembly variant of Yoga.

There are a lot of ways we can continue to improve this, but this merges the foundation. Subjectively, I find this more useful as a tool to play with Yoga behavior than the GUI.

This also replaces some of the bits of the homepage, and adds a playground entrypoint (though it's pretty identical to the one I've been testing on the home page).

Reviewed By: yungsters

Differential Revision: D51963201

fbshipit-source-id: 1265cb1784151b685686e189d47ecd42cbacdf8f

website-next/tsconfig.json

@@ -3,9 +3,8 @@
   "extends": "@docusaurus/tsconfig",
   "compilerOptions": {
     "baseUrl": ".",
-    "target": "esnext",
-    "module": "esnext",
-    "moduleResolution": "bundler",
-    "allowImportingTsExtensions": true
+    "target": "es2022",
+    "allowImportingTsExtensions": true,
+    "strict": true
   }
 }