MassInstallAction: Install the Downgrade workflow on this repository

[Krastanov]

This pull request sets up the Downgrade workflow on this repository. cc: @Krastanov

[Krastanov]

The value of having this in CI is to ensure you are not inadvertently depending on features available only in recent versions of your dependencies. It also helps against accidentally having your users resolve to an antiquated version of dependencies (that is not really checked in CI). For more info, check this discussion: https://discourse.julialang.org/t/psa-add-downgrade-ci-to-better-check-version-compatibility/110063 (I will add a newer version of this action that solves some resolver issues, available since Julia con and already used in the SciML ecosystem)

It has already detected broken lower compat bounds in other repos in JuliaGraphs

I am making this type of PRs to most of the JuliaGraphs repos. I do not have the capability to address the fact that this repo actually contains multiple packages that each need this to run separately for them. I am marking this as a draft and will not be pursuing it in the near term. Happy to help if there are any questions though. Hopefully this is helpful enough for the maintainers to finish adding such a check to CI.