Added eslint-plugin-jsx-a11y to install script

Author: chentsulin

packages/eslint-config-airbnb/README.md

@@ -11,9 +11,9 @@ We export three ESLint configurations for your usage.
 ### eslint-config-airbnb
 
 Our default export contains all of our ESLint rules, including EcmaScript 6+
-and React. It requires `eslint` and `eslint-plugin-react`.
+and React. It requires `eslint`, `eslint-plugin-react`, and `eslint-plugin-jsx-a11y`.
 
-1. `npm install --save-dev eslint-config-airbnb eslint-plugin-react eslint`
+1. `npm install --save-dev eslint-config-airbnb eslint-plugin-react eslint-plugin-jsx-a11y eslint`
 2. add `"extends": "airbnb"` to your .eslintrc
 
 ### eslint-config-airbnb/base