Add checkstyle and PMD plugin

[michalrys]

Checkstyle is a plugin for static analysis of code.

• Review this page: https://checkstyle.sourceforge.io/
• and intro: https://www.baeldung.com/checkstyle-java
• and description how to do it in Gradle: https://docs.gradle.org/current/userguide/checkstyle_plugin.html

It is also recommended to turn on PMD pluging for static analysis of code

• how to do it: https://docs.gradle.org/current/userguide/pmd_plugin.html

Implement it and connect also in github actions.