run tests on laravel 8 too

Author: melihovv

.github/workflows/default.yml

@@ -12,10 +12,12 @@ jobs:
     strategy:
       matrix:
         php: [7.4, 7.3, 7.2]
-        laravel: [7.*, 6.*]
+        laravel: [8.*, 7.*, 6.*]
         dependency-version: [prefer-lowest, prefer-stable]
         os: [ubuntu-latest, windows-latest]
         include:
+          - laravel: 8.*
+            testbench: 6.*
           - laravel: 7.*
             testbench: 5.*
           - laravel: 6.*