Add PHP 8.1 to CI

Author: ruudk

.github/workflows/continuous-integration.yml

@@ -53,6 +53,14 @@ jobs:
             php-version: "8.0"
             stability: "dev"
             symfony-deprecations-helper: "weak"
+          - dependencies: "php-http/guzzle7-adapter php-http/vcr-plugin:^1.0@dev"
+            php-version: "8.1"
+            stability: "dev"
+            symfony-deprecations-helper: "weak"
+          - dependencies: "php-http/guzzle7-adapter"
+            php-version: "8.1"
+            stability: "dev"
+            symfony-deprecations-helper: "weak"
 
           # Test maintained versions of Symfony
           - dependencies: "php-http/guzzle6-adapter"