document react development mode & add a way to override it

README.md

@@ -97,6 +97,12 @@ You may override our default debug option by providing your own `debug` key.
 }
 ```
 
+## React Development Mode
+
+When the `envName` for `babel` is `development`, [the `develoment` mode will be set for `@babel/preset-react`](https://babeljs.io/docs/en/babel-preset-react#development).
+
+To override this, set the `devEnv` option to a value that [`api.env`](https://babeljs.io/docs/en/next/config-files#apienv) accepts.
+
 ## React PropTypes removal
 
 This preset can be configured to remove propTypes using [babel-plugin-transform-react-remove-prop-types](https://github.com/oliviertassinari/babel-plugin-transform-react-remove-prop-types) with the following default options:

index.js

@@ -22,6 +22,8 @@ module.exports = declare((api, options) => {
 
   const debug = (options && typeof options.debug === 'boolean') ? !!options.debug : false;
 
+  const { devEnv = 'development' } = options || {};
+
   api.assertVersion(7);
 
   return {
@@ -36,7 +38,7 @@ module.exports = declare((api, options) => {
         modules: options.modules,
         targets: transpileTargets,
       }],
-      [require('@babel/preset-react'), { development: api.env('development') }],
+      [require('@babel/preset-react'), { development: api.env(devEnv) }],
     ],
     plugins: [
       options && !!options.removePropTypes ? ['babel-plugin-transform-react-remove-prop-types', assign({