add playground

Summary:
This adds a web-based playground to try out Yoga. The playground uses yogas javascript bindings to use yoga within the browser. The layout tree can be modified and shared. Code generators for litho, ComponentKit and React Native allow the layout to be copied into any app.

allow-large-files

Reviewed By: emilsjolander

Differential Revision: D6871601

fbshipit-source-id: 3b97c87e91d6bafe8e1c38b8b7eca8d372324c0b

playground/config-overrides.js

@@ -0,0 +1,17 @@
+const {injectBabelPlugin} = require('react-app-rewired');
+const rewireLess = require('react-app-rewire-less');
+
+module.exports = function override(config, env) {
+  config = injectBabelPlugin(
+    ['import', {libraryName: 'antd', style: true}],
+    config,
+  ); // change importing css to less
+  config = rewireLess.withLoaderOptions({
+    modifyVars: {
+      //'@primary-color': '#95ddcf',
+      '@font-family': 'Barlow',
+      '@grid-gutter-width': 15,
+    },
+  })(config, env);
+  return config;
+};