Merge branch 'rollup' of github.com:facebookexperimental/Recoil into rollup

package.json

@@ -26,6 +26,9 @@
   "devDependencies": {
     "@babel/core": "^7.9.6",
     "@babel/plugin-proposal-class-properties": "^7.8.3",
+    "@babel/plugin-syntax-optional-chaining": "^7.8.3",
+    "@babel/plugin-proposal-nullish-coalescing-operator": "^7.8.3",
+    "@babel/plugin-proposal-optional-chaining": "^7.9.0",
     "@babel/preset-flow": "^7.9.0",
     "@babel/preset-react": "^7.9.4",
     "@rollup/plugin-babel": "^5.0.0",

rollup.config.js

@@ -26,7 +26,17 @@ export default {
     format: 'cjs',
   },
   plugins: [
-    babel(),
+    babel({
+      "presets": [
+        "@babel/preset-react",
+        "@babel/preset-flow"
+      ],
+      "plugins": [
+        '@babel/plugin-proposal-nullish-coalescing-operator',
+        '@babel/plugin-proposal-optional-chaining',
+        '@babel/plugin-proposal-class-properties'
+      ]
+    }),
     nodeResolve(),
     commonjs(),
     //    includePaths(includePathOptions),