Add ability to put something in `<details>` section

[willmurphyscode]

What would you like to be added:

I'd like for all the dependabot and similar PRs that go into a release to be present in release notes, but collapsed by default.

Why is this needed:

1. Otherwise, a release that's mostly dependabot PRs would have no release notes at all
2. These PRs need to be collapsed by default or the release notes will noisy

Additional context: