Add PHP 8.1 support

SimonFrings · SimonFrings · commit 23326fa6f337 · 2021-11-12T13:50:19.000+01:00
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
@@ -10,9 +10,10 @@ jobs:
     strategy:
       matrix:
         os:
-          - ubuntu-latest
-          - windows-latest
+          - ubuntu-20.04
+          - windows-2019
         php:
+          - 8.1
           - 8.0
           - 7.4
           - 7.3
