Run sub-package tests on PHP 8.0 too (#1081)

Author: GrahamCampbell

.github/workflows/ci.yml

@@ -13,7 +13,7 @@ jobs:
     strategy:
       max-parallel: 10
       matrix:
-        php: ['7.2', '7.3', '7.4']
+        php: ['7.2', '7.3', '7.4', '8.0']
 
     steps:
       - name: Set up PHP