feat: Add flag for isFavorite

**Is your feature request related to a problem? Please describe.**
Most phones have the ability to "favorite" a contact to filter a larger list into a smaller set of closer contacts that the user often interacts with. Having this flag available in the data would be a useful projection to include.

**Describe the solution you'd like**
Most likely we would need to add a "favorite" projection to request the flag and then something as simple as isFavorite: boolean in the response

**Describe alternatives you've considered**
I've looked at the docs and pulled back all the info I can but it doesn't seem to exist with the existing dataset.

**Additional context**
I think this feature is useful for a variety of apps. For example if you were building an app where you wanted to invite people you could build at a list of "suggested invites" based on the users contacts. Or even building a better UI around the users contacts list to show the favorites at the top or with a particular UI element to distinguish them

Start by reviewing the contacts plugin's existing projections and returned contact data, then compare the available contact fields with the requested favorite flag. Done means the projection can request the favorite status and the response exposes it as an isFavorite boolean, with behavior verified across the supported contact data paths.

Written by the indexing model from the issue text.