Create inline annotations for found violations

[adangel]

GitHub supports to show annotations on the file tab of a pull request or when viewing a single commit.
This PMD Action should create for each found violation that is in the pmd-report.sarif file such an inline annotation. The rule priorities can be used to map to either a error, warning or notice message.

The result might look like this:

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Implementation notes:

• With Setting an error message GitHub Actions can create build annotations as errors, warnings or notice.
• The filename parameter probably needs to be relative to the repository root. With git rev-parse --show-toplevel one can figure out the current root checkout directory (which could be anywhere on the runner) and use that to make the absolute filepath in the sarif report into relative ones.