feat: check for dot platform org preset when onboarding

[rarkins]

Checks for a renovate.json file in a repo like org/.github and uses it during onboarding if found.

Closes #7422

[rarkins]

@viceice @ljharb there's maybe one or two downsides to this. The ".github" repo itself then must use the same renovate.json for its own config and hence can't modify it or else all other repos will get the modifications passed on.

A second problem is maybe someone already has a .github repo and want to renovate it and so has a renovate.json already and it's not suitable for extending to all onboarding repos?

These are probably not problems in the majority of cases, but another alternative would be to use a different file name like renovate-config.json or renovate-org-config.json instead.

[viceice]

Ok, so I suggest to use an other filename like renovate-config.json. otherwise LGTM

[ljharb]

Agreed; another filename makes sense.

Also, .github repos typically allow files either in the root, or in the .github repo's .github directory.

[renovate-release]

🎉 This PR is included in version 23.44.0 🎉

The release is available on:

• GitHub release
• 23.44.0

Your semantic-release bot 📦🚀