chore: added php 8.0 into testing matrix

Author: alexsoft

.github/workflows/tests.yml

@@ -10,7 +10,7 @@ jobs:
         strategy:
             fail-fast: true
             matrix:
-                php: [7.2, 7.3, 7.4]
+                php: [7.2, 7.3, 7.4, 8.0]
                 stability: [prefer-lowest, prefer-stable]
 
         name: Tests on PHP ${{ matrix.php }} - ${{ matrix.stability }}