Docusarus: Init Project

Summary:
This starts us transitioning the Yoga website off of an ancient version of Gatsby by initializing a new Docusaurus project. This commit adds a new stock project, to be filled in later, then fixes license lint errors.

Note that this seems to have init'd using npm, but in the next diff I convert this to yarn workspaces anyway.

Reviewed By: yungsters

Differential Revision: D46884434

fbshipit-source-id: ee388aa9388b1030dbbf59a73dd1529fee05065c

website-next/tsconfig.json

@@ -0,0 +1,7 @@
+{
+  // This file is not used in compilation. It is here just for a nice editor experience.
+  "extends": "@tsconfig/docusaurus/tsconfig.json",
+  "compilerOptions": {
+    "baseUrl": "."
+  }
+}