Implement Content Git Repository API

[kmasiello]

Implement GET and PUT wrappers to view and modify the git repository settings for content.

Will greatly improve recipe at posit-dev/connect-cookbook#57

API Proposal

from posit import connect

client = connect.Client()
content = client.content.get(...)
repository = content.repository or content.create_repository(...) # GET or POST
repository.update(...) # PATCH
repository.delete() # DELETE

[zackverham]

@tdstein I can try to pick this one up as sand work!

[schloerke]

Closed in #300