Run the tests on CI with all warnings enabled

This allows us to catch things that will break in future PHP versions,
but still kind-of-work, e.g., deprecation warnings or incorrect types.

Author: oliverklee

.github/workflows/ci.yml

@@ -53,6 +53,7 @@ jobs:
         uses: shivammathur/setup-php@v2
         with:
           php-version: ${{ matrix.php-version }}
+          ini-values: error_reporting=E_ALL
           tools: composer:v2
           coverage: "${{ matrix.coverage }}"