add codecov badge

.github/workflows/phpunit.yml

@@ -56,4 +56,10 @@ jobs:
         run: "composer install --no-interaction --no-progress --no-suggest"
 
       - name: "Tests"
-        run: "vendor/bin/phpunit"
+        run: "XDEBUG_MODE=coverage vendor/bin/phpunit --coverage-clover coverage.xml"
+
+      - name: "Send codecov report0"
+        uses: codecov/codecov-action@v1
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }} # not required for public repos
+          files: ./coverage.xml

README.md

@@ -1,6 +1,7 @@
 # Pheature Flags Toggle Core
 
 [![Type coverage][ico-psalm]][link-psalm]
+[![Maintainability][ico-mantain]][link-mantain]
 
 Pheature flags toggle core library, take a look to our [main package]() to see our roadmap and project status.
 
@@ -27,3 +28,5 @@ knowledge to the community. For this reason we release all our packages under [B
 
 [ico-psalm]: https://shepherd.dev/github/pheature-flags/toggle-core/coverage.svg
 [link-psalm]: https://shepherd.dev/github/pheature-flags/toggle-core
+[ico-mantain]: https://codecov.io/gh/pheature-flags/toggle-core/branch/1.0.x/graph/badge.svg?token=DTQIQUZ106 
+[link-mantain]: https://codecov.io/gh/pheature-flags/toggle-core