Support remote interface

Especially when running in container it would be very nice to be able to start things only as remote library.

I think command would work fine, and only "harder" part would be the screenshot handling. But that's probably also quite easy because those are just strings.

Example: https://github.com/robotframework/PythonRemoteServer/tree/master/example

Start by comparing the requested remote-library mode with the PythonRemoteServer example linked in the issue, then inspect how the library is currently started and how screenshot handling works. Done means the library can run remotely, including screenshot responses, in a containerized setup.

Written by the indexing model from the issue text.