feature: allow to change rgb value on Seriously.js via config

[andi34]

Is your feature request related to a problem? Please describe.

Green screen might have a different green color, keying result depends on it.

Describe the solution you'd like

Allow to adjust the rgb value via config inside the Adminpanel.

Describe alternatives you've considered

Additional context

I'll take a look at once I have enough time. Making the values a config can be done quickly, slider for each value, range Config from 0-255, steps 1.

Maybe we can add a small preview of the green color?

[jacques42]

Closed via PR #213