add PHP 8 to GitHub workflow so we can test

Author: michaeldyrynda

.github/workflows/run-tests.yml

@@ -12,8 +12,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php: [7.4, 7.3]
-        laravel: [^8.0]
+        php: [8.0, 7.4, 7.3]
+        laravel: [^8.12]
         dependency-version: [prefer-lowest, prefer-stable]
         os: [ubuntu-latest]