Update README.md

Author: tabacitu

README.md

@@ -65,7 +65,7 @@ Alternatively, if you don't have 20 minutes right now, subscribe to our [drip em
 ## Install
 
 Installation guides:
-- [Install Backpack 4.0 on Laravel 6](https://backpackforlaravel.com/docs/4.0/installation) - recommended
+- [Install Backpack 4.0 on Laravel 5.8, 6 or 7](https://backpackforlaravel.com/docs/4.0/installation) - recommended
 - [Install Backpack 3.6 on Laravel 5.8 or 6.x](https://backpackforlaravel.com/docs/3.6/installation) - last feature update was 17th Sep 2019;
 - [Install Backpack 3.5 on Laravel 5.5, 5.6, 5.7](https://backpackforlaravel.com/docs/3.5/installation) - last feature update was 27th Feb 2019;
 - [Install Backpack 3.x on Laravel 5.4](https://laravel-backpack.readme.io/docs/install-on-laravel-54) - last feature update was 27 Sep 2017;