general: add screen cast border indicators

[xavi-b]

Describe your PR, what does it fix/add?

Add options to enable and set a color around windows or monitors when they are screencasted.

Is there anything you want to mention? (unchecked code, possible bugs, found problems, breaking compatibility, etc.)

I did not know how to name the options and/or which categories to put them in.

Is it ready for merging, or does it need work?

Options names and categories could be changed.

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[vaxerski]

it will show up in the recording. Idk if this is a good idea.

Furthermore, what about screenshots? You should probably restrict this to the flow of screencopy

[xavi-b]

You should probably restrict this to the flow of screencopy

Sorry to bother you but could you explain a bit more ?

So far, I have only found a way to add "layers" on what the screen copy will render.
But I could not find a way to render something only on the monitor but not on the screen copy.

Any hints ?

[vaxerski]

you cant in a simple way atm