Meta tag support for commerce_store entity type

Created a small patch to allow adding defaults to the commerce_store entity type.

While the patch needs to be turned into a merge request so we can run the tests to make sure there aren't any regressions, I think this is a worthwhile change and we'll include it in the next feature release. Thank you!

Hey, I just created an MR with the patch from #2, I also added an unit test for the getSupportedEntityTypes, I know it seems out of the scope, but I think the unsupported entities can change in the future, so to add some coverage there I though it could be a good idea to cover it with tests, I also would like to add more coverage to the MetatagDefaultsForm class, but I think this would increase the solution here, and we can address this in a separate issue. I'm moving this back to NR to see what you guys think about it.

Committed. Thank you!

Automatically closed - issue fixed for 2 weeks with no activity.