fix phpunit version, add php versions to tests

Author: thekonz

.editorconfig

@@ -6,3 +6,6 @@ end_of_line = lf
 indent_size = 4
 indent_style = space
 insert_final_newline = true
+
+[*.yml]
+indent_size = 2

.github/workflows/ci.yml

@@ -6,8 +6,18 @@ jobs:
   build-test:
     runs-on: ubuntu-latest
 
+    strategy:
+      matrix:
+        php-versions:
+          - 7.2
+          - 7.3
+          - 7.4
+
     steps:
       - uses: actions/checkout@v2
+      - uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php-versions }}
       - uses: php-actions/composer@v1
       - name: PHPUnit Tests
-        uses: php-actions/phpunit@v9
+        uses: php-actions/phpunit@v8