Added Codecov for unit testing

Author: rennokki

.github/workflows/run-tests.yml

@@ -45,4 +45,8 @@ jobs:
                     composer update --${{ matrix.dependency-version }} --prefer-dist --no-interaction --no-suggest
 
             -   name: Execute tests
-                run: vendor/bin/phpunit
+                run: vendor/bin/phpunit --coverage-text --coverage-clover=coverage.xml
+
+            -   uses: codecov/codecov-action@v1
+                with:
+                    fail_ci_if_error: false