Toggle text from black to white with a double-click on the GUI

[darksidelemm]

Forcing the text to be either black or white doesn't work for in-flight streaming with cloud. The operator really needs to be able to change the text between black or white on demand.
Suggest doing this via a double-click on the GUI, which is easy to do while live-streaming.

Alternatively a 'stroke' around the text would work too, but I'm not sure how possible this is with PyQt5... maybe some other GUI library is needed...