Fix broken rule reference link import/first

Author: 1pete

README.md

@@ -1239,7 +1239,7 @@ Other Style Guides
 
   <a name="modules--imports-first"></a>
   - [10.7](#modules--imports-first) Put all `import`s above non-import statements.
- eslint: [`import/imports-first`](https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/imports-first.md)
+ eslint: [`import/first`](https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/first.md)
     > Why? Since `import`s are hoisted, keeping them all at the top prevents surprising behavior.
 
     ```javascript