add php 8.x to github workflows

.github/workflows/main.yml

@@ -8,7 +8,7 @@ jobs:
     strategy:
       matrix:
         operating-system: [ubuntu-latest]
-        php-versions: ['8.0']
+        php-versions: ['8.0', '8.1', '8.2']
         include:
           - operating-system: 'ubuntu-18.04'
             php-versions: '7.0'