test: add pre-commit hook for helm-docs

[morremeyer]

With this change, users of pre-commit can register a pre-commit hook that automatically
runs helm-docs when a chart changes.

This saves contributors such as me from forgetting to run helm-docs every single time
they commit if they want to do so.

[rlex]

I thought about implementing helm-docs as a part of CI pipeline, but maybe having both options is good idea

[morremeyer]

We could add pre-commit lite action (https://pre-commit.ci/lite.html), this would run pre-commit and commit the fixes.

That way, if any other linters or doc generators are added later, they are automatically run, too.

What do you think?

[rlex]

I never commited anything from CI, wonder how it will appear in commit history? From github internal user?

[morremeyer]

Depends on the user creating the commit.

If you check morremeyer/charts, you'll see commits from a bot user (not an app!) that we use in that repo.

With pre-commit lite, it will appear as the app user. In that case pre-commit-ci-lite (bot).