Add API endpoint for getting camera image from KSP

[tcannonfodder]

GoAtThrottleUp, an outdated flight data mod, had an endpoint for getting a screenshot of a camera. I think an API endpoint for getting a camera would be a great addition to Telemachus, allowing mission control tools to embed "live feeds" in stations.

The code in GoAtThrottleUp is here: https://github.com/TheTacoScott/GoAtThrottleUp/blob/master/Plugin/GoAtThrottleUpCamera.cs