chore: categorize dependency updates and other changes in auto-generated release notes

[pddg]

Release note of grafana-operator seems to be generated by GitHub's auto-generation feature.
https://docs.github.com/en/repositories/releasing-projects-on-github/automatically-generated-release-notes

It is hard for us to read large number of changes that may contains important changes.
Special attention should be paid when important changes are mixed in with the large number of dependency change logs.

Fortunately, the PRs automatically generated by dependabot are labeled dependencies. This could be used to categorize the list of changes in the release notes to reduce the burden on the user.
https://docs.github.com/en/repositories/releasing-projects-on-github/automatically-generated-release-notes#configuration-options

The release notes should now appear as follows:

## What's Changed

### Changes

- chore: some update by @~~  in #123
- some important changes by @~~ in #456

### Dependencies

- chore(deps): bump ~~ by @dependabot in #789

The category titles are tentative, so if you have a good one, please let me know.

[CLAassistant]

All committers have signed the CLA.

[weisdd]

@pddg thanks for the PR!

Indeed, it makes sense to categorize changes in release descriptions. It's actually something that we briefly discussed (internally) quite a while ago, just have never implemented it ourselves due to being busy with other things.

As for the titles, I think we can leave as is for now. Later, if we start adding more labels to PRs at some point, we can further improve the layout / titles.

Let's see what other maintainers think. - We'll probably discuss it on Monday.