Update package to support Laravel 8

[Daniel-I-Am]

Related to #41

This PR is to update the plugin to be compatible with the most recent release of Laravel. Not to implement the new and awesome features that come packed with it, like Blade Components or Jetstream.

Functionality tested

The following list of actions has been tested by running them in a fresh project. laravel new test-project

• [x] Publishing assets
• [x] Running ui:coreui
• [x] Publishing and editing coreui config
• [x] Gate functionality
• [x] Publishing and editing coreui view
• [x] Publishing and editing coreui language files

Changelog

• Change composer requirements.
  • Change php ^7.2 => php ^7.3
  • Change laravel/framework ^6.0 => laravel/framework ^8.0.
  • Add laravel/ui ^3.0.
• Change ui:coreui command to also run ui:controllers
• Change format of src/Console/stubs/routes.stub to be functional with Laravel 8