Add skeleton for documentation (#1589)

Summary:
Pull Request resolved: https://github.com/facebook/yoga/pull/1589

Adds a skeleton to the new website of documentation and such for us to fill out.

Reviewed By: joevilches

Differential Revision: D54567186

fbshipit-source-id: 700dfe0787fcb9806c3daa0675e838540119bbc0

website-next/src/pages/index.tsx

@@ -24,7 +24,9 @@ function HeroSection() {
             A portable layout engine targeting web standards
           </p>
 
-          <Link className="button button--primary button--lg" to="/docs/intro">
+          <Link
+            className="button button--primary button--lg"
+            to="/docs/about-yoga">
             Learn more
           </Link>
         </div>