adding github actions

.github/workflows/tests.yml

@@ -0,0 +1,38 @@
+name: PHP Composer
+
+#whenever master has a PR or is pushed to
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  run:
+    runs-on: ubuntu-18.04
+    strategy:
+      #for each of the following versions of PHP, with and without --prefer-lowest
+      matrix:
+        php-versions: ['5.5', '5.6', '7.0', '7.1', '7.2', '7.3', '7.4']
+
+    #set the name for each job
+    name: PHP ${{ matrix.php-versions }}
+    steps:
+      #sets up the correct version of PHP with necessary config options
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php-versions }}
+          ini-values: memory_limit=4G, phar.readonly=false
+
+      #checkout the codebase from github
+      - name: Checkout codebase
+        uses: actions/checkout@v3
+
+      #run composer
+      - name: Composer install
+        run: composer install
+
+      #run tests
+      - name: Run test suite
+        run: vendor/bin/phpunit