chore: ignore files generated on mvn package

[KClough]

Summary:

While building on OSX, we noticed a number of files are generated and should not be included in source control.

Expected behavior:

Building and running the realtime validator locally should not create untracked files.

• [x] Run the unit tests with mvn test to make sure you didn't break anything
• [x] Format the title like "feat: {new feature short description}" or "fix: {describe what was fixed}". Title must follow the Conventional Commit Specification (https://www.conventionalcommits.org/en/v1.0.0/).
• [x] Linked all relevant issues
• [] Include screenshot(s) showing how this pull request works and fixes the issue(s)

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