Move react-docgen to peer dependencies

Author: thompsonsj

README.md

@@ -31,3 +31,25 @@ storiesOf('Button')
   .add('simple', () => <Button>Smart knobed button</Button>)
 
 ```
+
+## Configuration:
+
+This plugin has a peer dependency on [babel-plugin-react-docgen
+](https://github.com/storybooks/babel-plugin-react-docgen). As a result, `babel-plugin-react-docgen` needs to be added to your Storybook Babel configuration.
+
+For a standard Storybook configuration, add `react-docgen` to your plugins in an appropriate `.babelrc` file.
+
+  - [README | babel-plugin-react-docgen](https://github.com/storybooks/babel-plugin-react-docgen/blob/master/README.md)
+  - [Custom Babel Config | Storybook](https://storybook.js.org/configurations/custom-babel-config/).
+
+If you have created a `webpack.config.js` file for Storybook, you may need to configure the plugin in there.
+
+```
+module.exports = (baseConfig, env, defaultConfig) => {
+  defaultConfig.module.rules[0].use[0].options.plugins = [
+    require.resolve('babel-plugin-react-docgen'),
+  ]
+
+  return defaultConfig
+}
+```

package.json

@@ -27,7 +27,6 @@
     "@storybook/addon-options": "^4.1.1",
     "@storybook/react": "^4.1.1",
     "babel-loader": "^8.0.4",
-    "babel-plugin-react-docgen": "^2.0.0",
     "css-loader": "^2.0.0",
     "eslint-config-taller": "^2.0.0",
     "eslint-plugin-flowtype": "^3.0.0",
@@ -41,6 +40,7 @@
     "@storybook/addon-knobs": "^4.1.1",
     "@storybook/addon-options": "^4.1.1",
     "@storybook/react": "^4.1.1",
+    "babel-plugin-react-docgen": "^2.0.0",
     "react": ">=15.0.0 || ^16.0.0"
   }
 }