enable PHP 8.5 for testing

.github/workflows/tests.yml

@@ -27,11 +27,11 @@ jobs:
     continue-on-error: "${{ matrix.experimental }}"
     strategy:
       matrix:
-        php-versions: ['7.4', '8.0', '8.1', '8.2', '8.3', '8.4']
+        php-versions: ['7.4', '8.0', '8.1', '8.2', '8.3', '8.4', '8.5']
         experimental: [false]
 # uncomment this to start testing on development release
 #        include:
-#          - php-versions: '8.5' # development release, things can break
+#          - php-versions: '8.6' # development release, things can break
 #            experimental: true
     env:
       extensions: gd, sqlite3