Widgets: Idea: Add a screen-based joypad

[RaulTrombin]

Something similar to: https://bobboteck.github.io/joy/joy.html

But also with a slider bar to control zoom and focus:

It could even be used to control the ROV using two of then on the botton side with mobile devices.

[rafaellehmkuhl]

This would be valuable for overall vehicle control also!

We should have that, yes. For that we need to change our structure a little bit to be able to accept inputs for things other than the Gamepad API.

[ES-Alexander]

Potentially relevant to #1291