Add formatter cache directory to .gitignore

[dmlloyd]

No description provided.

[gastaldi]

Nice catch. Make sure to also update the formatter plugin to 2.12.1, so this directory will only be created if it did not actually write any files for update within the cache

See https://github.com/revelc/formatter-maven-plugin/blob/formatter-maven-plugin-2.12.1/CHANGELOG.md#ver-2121

[dmlloyd]

I think that part would have to be done on smallrye-parent. I'll check into it.

[dmlloyd]

Yep the parent is already updated, so that will come through when dependabot comes with the update.

[dmlloyd]

I'm merging manually, because the build will never run due to the change being made to an ignored file.