Add fmt to check target

[belimawr]

What does this PR do?

Add fmt to check target

Why is it important?

Because fmt was not part of mage check, the code was not correctly formatted and running mage fmt on a new branch/PR would generate many unrelated changes. #363 already formatted the code, now this PRs ensures we do it on every PR.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have added tests that prove my fix is effective or that my feature works

## Author's Checklist

Related issues

• Follow up from [chore] Fix mage fmt and reformat code #363

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: fa860bb

cc @belimawr