laravel: add README (#7222)

plugins/laravel/README.md

+# Laravel plugin
+
+This plugin adds aliases and autocompletion for Laravel [Artisan](https://laravel.com/docs/artisan) and [Bob](http://daylerees.github.io/laravel-bob/) command-line interfaces.
+
+**NOTE:** completion might not work for recent Laravel versions since it hasn't been updated since 2012.
+In that case, check out plugins `laravel4` and `laravel5`.
+
+To use it, add `laravel` to the plugins array in your zshrc file:
+
+```zsh
+plugins=(... laravel)
+```
+
+## Aliases
+
+| Alias     | Command                  | Description          |
+|-----------|--------------------------|----------------------|
+| artisan   | `php artisan`            | Main Artisan command |
+| bob       | `php artisan bob::build` | Main Bob command     |