message: Update  15-dot-env readme
diff: @@ -74,7 +74,7 @@ module.exports = merge(common, {
  - Let's setup the plugin prod config.
  -_./webpack.prod.config.js_
  +_./webpack.prod.js_
  ```diff
  const merge = require("webpack-merge");
  @@ -82,7 +82,7 @@ const common = require("./webpack.common.js");
  + const Dotenv = require('dotenv-webpack');
  ```
  -_./webpack.prod.config.js_
  +_./webpack.prod.js_
  ```diff
  const merge = require("webpack-merge");
  