Sonarqube reports inaccurate stats

- No code coverage information https://sonarcloud.io/code?id=hCaptcha_HCaptcha-ios-sdk
- Most of the issues related to `_` in test function names
- Add badge [![Quality Gate Status](https://sonarcloud.io/api/project_badges/measure?project=hCaptcha_HCaptcha-ios-sdk&metric=alert_status)](https://sonarcloud.io/summary/new_code?id=hCaptcha_HCaptcha-ios-sdk)