Move yoga docs into docs folder on master branch

Summary: Move yoga docs into master branch so that pull requests are able to include doc updates as part of other changes.

Reviewed By: JoelMarcey

Differential Revision: D4365700

fbshipit-source-id: 2f46a88974104c454c00bcdf1257abb5c4075a68

docs/_sass/_promo.scss

@@ -0,0 +1,55 @@
+.promoSection {
+  display: flex;
+  flex-flow: column wrap;
+  font-size: 125%;
+  line-height: 1.6em;
+  margin: -10px 0;
+  position: relative;
+  z-index: 99;
+
+  .promoRow {
+    padding: 10px 0;
+
+    .pluginWrapper {
+      display: block;
+
+      &.ghWatchWrapper, &.ghStarWrapper {
+        height: 28px;
+      }
+    }
+
+    .pluginRowBlock {
+      display: flex;
+      flex-flow: row wrap;
+      margin: 0 -2px;
+
+      .pluginWrapper {
+        padding: 0 2px;
+      }
+    }
+  }
+}
+
+iframe.pluginIframe {
+  height: 500px;
+  margin-top: 20px;
+  width: 100%;
+}
+
+.iframeContent {
+  display: none;
+}
+
+.iframePreview {
+  display: inline-block;
+  margin-top: 20px;
+}
+
+@media only screen and (min-width: 1024px) {
+  .iframeContent {
+    display: block;
+  }
+  .iframePreview {
+    display: none;
+  }
+}