maint: use php 8.2 for GitHub action

Author: roydejong

.github/workflows/phpunit.yml

@@ -10,6 +10,12 @@ jobs:
     steps:
       - uses: actions/checkout@v2
 
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: 8.2
+          extensions: curl, json, mbstring, openssl
+
       - name: Validate composer.json and composer.lock
         run: composer validate