Run tests on PHP 8.4 and update test environment

Author: PaulRotmann

.github/workflows/ci.yml

@@ -7,10 +7,12 @@ on:
 jobs:
   PHPUnit:
     name: PHPUnit (PHP ${{ matrix.php }})
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     strategy:
       matrix:
         php:
+          - 8.4
+          - 8.3
           - 8.2
           - 8.1
           - 8.0
@@ -39,7 +41,7 @@ jobs:
 
   PHPUnit-hhvm:
     name: PHPUnit (HHVM)
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-24.04
     continue-on-error: true
     steps:
       - uses: actions/checkout@v2