Update matrix to be more specific

Author: marickvantuil

.github/workflows/run-tests.yml

@@ -36,7 +36,11 @@ jobs:
             php: 7.4
           - laravel: 5.5.*
             php: 7.4
-          - laravel: 5.*
+          - laravel: 5.8.*
+            php: 8.0
+          - laravel: 5.7.*
+            php: 8.0
+          - laravel: 5.6.*
             php: 8.0
 
     name: PHP ${{ matrix.php }} - Laravel ${{ matrix.laravel }}