Add PHP 8.1 to GitHub Actions workflows

Author: jbelien

.github/workflows/component.yml

@@ -13,7 +13,7 @@ jobs:
  strategy:
  fail-fast: false
  matrix:
- php-version: ['7.3', '7.4', '8.0']
+ php-version: ['7.3', '7.4', '8.0', '8.1']
  steps:
  - uses: actions/checkout@v2
  - name: Use PHP ${{ matrix.php-version }}