Define Checkstyle and PMD rules

[karianna]

Above changes will not break in github workflow. But we add following commands in workflow, this will fail workflow, we might to have correct error first.

• mvn checkstyle:check Failed to execute goal org.apache.maven.plugins:maven-checkstyle-plugin:3.1.2:check (default-cli) on project api: You have 2838 Checkstyle violations
• mvn spotbugs:check Failed to execute goal com.github.spotbugs:spotbugs-maven-plugin:4.3.0:check (default-cli) on project api: failed with 81 bugs and 0 errors

Ah I see - so we need to define the project stds for checkstyle and PMD! :-)

Originally posted by @karianna in https://github.com/microsoft/gctoolkit/issues/33#issuecomment-897158855

[karianna]

Ii think the core committers should have the initial say here - but worth defining!

[dsgrieve]

We should probably center on Google's style since it is IDE neutral, is actively maintained, and there are reformatting tools available.

[ghost]

completed