Docusarus: Init Project (#1312)

Summary:
Pull Request resolved: https://github.com/facebook/yoga/pull/1312

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: 7a0a4dddc144ad2d22cd18a02e8dcb9ff2184489

website-next/docs/tutorial-basics/create-a-blog-post.md

@@ -0,0 +1,34 @@
+---
+sidebar_position: 3
+---
+
+# Create a Blog Post
+
+Docusaurus creates a **page for each blog post**, but also a **blog index page**, a **tag system**, an **RSS** feed...
+
+## Create your first Post
+
+Create a file at `blog/2021-02-28-greetings.md`:
+
+```md title="blog/2021-02-28-greetings.md"
+---
+slug: greetings
+title: Greetings!
+authors:
+  - name: Joel Marcey
+    title: Co-creator of Docusaurus 1
+    url: https://github.com/JoelMarcey
+    image_url: https://github.com/JoelMarcey.png
+  - name: Sébastien Lorber
+    title: Docusaurus maintainer
+    url: https://sebastienlorber.com
+    image_url: https://github.com/slorber.png
+tags: [greetings]
+---
+
+Congratulations, you have made your first post!
+
+Feel free to play around and edit this post as much you like.
+```
+
+A new blog post is now available at [http://localhost:3000/blog/greetings](http://localhost:3000/blog/greetings).