docs(README): change bootstrap path in example (#438)

Author: chukitow

README.md

@@ -120,7 +120,7 @@ module.exports = {
 webpack provides an [advanced mechanism to resolve files](https://webpack.js.org/concepts/module-resolution/). The sass-loader uses node-sass' custom importer feature to pass all queries to the webpack resolving engine. Thus you can import your Sass modules from `node_modules`. Just prepend them with a `~` to tell webpack that this is not a relative import:
 
 ```css
-@import "~bootstrap/css/bootstrap";
+@import "~bootstrap/dist/css/bootstrap";
 ```
 
 It's important to only prepend it with `~`, because `~/` resolves to the home directory. webpack needs to distinguish between `bootstrap` and `~bootstrap` because CSS and Sass files have no special syntax for importing relative files. Writing `@import "file"` is the same as `@import "./file";`