Add checkstyle #98
Description
As a developer, I want to add checkstyle code quality stage to GitHub actions before code build.
Acceptance:
- warnings will be treated as errors
- use the latest google style template up to date, if needed we will adapt rules to our team style:
https://github.com/checkstyle/checkstyle/blob/master/src/main/resources/google_checks.xml - add maven pom.xml dependencies and plugin config
- add GitHub action stage