chore: Use Dependabot groups to bundle PRs

[nschonni]

Potentially this could just be one big blob of updates of prod+dev, but I thought splitting it might make sense. This way, the next time there is a ton of remark-lint bumps, we'll only get one PR.
I flipped the cadence for NPM PRs to weekly, since I don't know if there is a need for daily PRs, even with the bundled updates.

[Trott]

I'm not opposed to this, but it is worth mentioning that the last time we had a bunch of remark-lint-* updates, there were two or three that couldn't land, so there was arguably benefit to getting them one at a time so you could readily identify which ones were failing and land all the other ones before troubleshooting the ones with breaking changes.

That said, this won't make identifying issues impossible or anything like that, and the convenience for the happy path/typical case might be worth the small cost when there's a problem.

[nschonni]

@Trott I have similar concerts about tracing down what's broken too. I've landed it to give it a try, but if it doesn't work out, we can easily revert it