Create staging deployments for all PRs, not just PRs into the deployment branch

[kathweinschenkprophecy]

The staging deployments in PRs are extremely useful for reviewers.

Currently, staging deployments are only triggered when you open a PR into the deployment branch of your repo.

Our team's workflow is: main > release branch > working branches, so we don't see previews for our working branches.

I would like to either have to ability to edit the managed deployment action OR for there to be a toggle in settings that allows us to enable previews on ALL PRs. This would help us a lot!

[tillrohrmann]

We would love to have this feature as well as it would allow us to have a staging area where we collect changes for an upcoming release.