Adds dependabot config.
Seems like monthly is the least frequent update you can choose right now
(there are feature request for quarterly and for chron like syntax).
For now I used the daily interval though. I want to make sure it works,
will then switch to monthly. The main thing I'd like to see is that the
main `yarn.lock` file gets updated. That didn't happen in one of the
previous dependabot PRs (seems like [others faced the same
issue](https://github.com/dependabot/dependabot-core/issues/6346)). So 🤞
this solves it.
Also added a dedupe workflow, that should only run on dependabot
branches (prefixed with `depandabot/`). Otherwise we would need to
manually do it, as [seen on this
PR](https://github.com/tldraw/tldraw/pull/2982)
([failure](https://github.com/tldraw/tldraw/actions/runs/8070271847/job/22047204003)).
### Change Type
- [ ] `patch` — Bug fix
- [ ] `minor` — New feature
- [ ] `major` — Breaking change
- [ ] `dependencies` — Changes to package dependencies[^1]
- [ ] `documentation` — Changes to the documentation only[^2]
- [ ] `tests` — Changes to any test code only[^2]
- [x] `internal` — Any other changes that don't affect the published
package[^2]
- [ ] I don't know
[^1]: publishes a `patch` release, for devDependencies use `internal`
[^2]: will not publish a new version
