Update package description

No code changes, just removing "Laravel 6" from package description.

Backpack V4.1 support

This release adds support for Backpack 4.1
tagged 3.0.0 because Backpack api has some breaking changes in its api.
it doesn't have any other change that might affect you like database structure or class/method renaming.

Update Readme

Improve documentation in readme

Backpack V4 compatibility

Fixed bugs and removed code that was only useful with V3

Backpack 4 Support

This version only supports Backpack 4

Initial version

Based on https://github.com/Laravel-Backpack/PermissionManager