Make documentation embeds less ugly (#1670)

Summary:
Pull Request resolved: https://github.com/facebook/yoga/pull/1670

Embeds to Yoga's documentation reuse a tiny rasterized favicon, blown up, and full of jpeg artifacts.

{F1714492025}

This bothered me enough to make the previews look better.

This change adds a quickly whipped up opengraph sized image, replaces the favicon with one derived from logo SVG, and fixes a missing description on the homepage.

 {F1714566402}

Reviewed By: yungsters

Differential Revision: D58923501

fbshipit-source-id: 249a23034f50667e32970121a90eccc380e566a3

website/src/pages/index.tsx

@@ -76,7 +76,7 @@ function PlaygroundSection() {
 
 export default function Home(): JSX.Element {
   return (
-    <Layout>
+    <Layout description="Documentation for the Yoga layout engine">
       <HeroSection />
       <PlaygroundSection />
     </Layout>