feat: add .gitignore and README.md support to manta-parameters

[bhgomes]

Signed-off-by: Brandon H. Gomes bhgomes@pm.me

Adds .gitignore support for manta-parameters. Files can now be added to the data directory without requiring them to be uploaded to GitHub by specifying them in a .gitignore file local to any of the subdirectories of the data directory. In this case, a README.md should be used to direct users to download the ignored files from an external service.

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Before we can merge this PR, please make sure that all the following items have been checked off:

• Linked to an issue with discussion and accepted design OR have an explanation in the PR that describes this work.
• Added one line describing your change in CHANGELOG.md and added the appropriate changelog label to the PR.
• Re-reviewed Files changed in the GitHub PR explorer.
• Checked that changes and commits conform to the standards outlined in CONTRIBUTING.md.
• Ran cargo hakari generate to update the workspace-hack system

[SupremoUGH]

It all seems fine, but have you checked that it works with an actual file?

[bhgomes]

It all seems fine, but have you checked that it works with an actual file?

Yes, I've checked it. @GhostOfGauss you should also check that it matches your workflow to make sure that these changes make sense.

[GhostOfGauss]

Looks good to me