Show return type annotation when show_signature_annotations = true #4

Describe the solution you'd like

When setting:

plugins:
  - search
  - mkdocstrings:
      handlers:
        python:
          rendering:
            show_signature_annotations: true

It would be helpful if this also rendered the return type (e.g -> int)

This is the common, concise way that Python developers are used to reading types.

Describe alternatives you've considered

An extra configuration option, but I don't think that is necessary.