docs: Clarifying babel/webpack docs (#1845)

docs/jsx.md

@@ -98,7 +98,7 @@ npm install babel-core babel-loader babel-preset-es2015 babel-plugin-transform-r
 
 Create a `.babelrc` file:
 
-```
+```json
 {
 	"presets": ["es2015"],
 	"plugins": [
@@ -130,6 +130,8 @@ module.exports = {
 }
 ```
 
+For those familiar with Webpack already, please note that adding the Babel options to the `babel-loader` section of your `webpack.config.js` will throw an error, so you need to include them in the separate `.babelrc` file.
+
 This configuration assumes the source code file for the application entry point is in `src/index.js`, and this will output the bundle to `bin/app.js`.
 
 To run the bundler, setup an npm script. Open `package.json` and add this entry under `"scripts"`: