add PHP8.1 to CI

Author: baohx2000

.github/workflows/build.yml

@@ -12,7 +12,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php: [7.3, 7.4, 8.0]
+        php: [7.3, 7.4, 8.0, 8.1]
 
     name: PHP ${{ matrix.php }}
     steps: