🔧 Repository: Make backstage/community-plugins workflows more easily repeatable (with tooling)

Some Backstage plugin developers I have spoken to have mentioned they'd a setup like `backstage/community-plugins` for their internal plugin development. I've also heard some are already using this structure as inspiration for their initial workflows.

This issue is to propose making community plugins tooling more consumable and repeatable for plugin developers.

For now, it is possible to reuse the workflows in the repository, however, I believe they're not as consumable as they could be. Some possible enhancements/ideas I've thought of:

* Identifying/isolating 'mandatory/required' workflows from additional workflows (such as Renovate, PR sync, etc.)
* Documentation on what GitHub/npm/user accounts are required by the workflows.
* Make `@backstage-community/repo-tools` end-user facing, perhaps publishing as a package.
* Some mechanism to keep workflows up-to-date.
* Some tooling like `npx @backstage-community/repo-tools create-repository` to generate the mandatory/needed workflows and structure.

This is something I believe would be pretty valuable, and create a common default pattern for plugin development.

### Are you willing to submit PR?

Yes I am willing to submit a PR!

Start by reviewing the repository's existing workflows and the @backstage-community/repo-tools package, separating mandatory workflows from optional ones. Compare the possible account documentation, package publishing, update mechanism, and npx create-repository ideas before defining a focused scope and acceptance criteria.

Written by the indexing model from the issue text.