Feature request: Linux Compatibility

[rDarge]

Referenced in #1 , there are some changes that need to be made to allow for non-windows platforms to compile and run VGT. I briefly had it working on both Linux and Mac, but since I no longer have access to Apple hardware, I'd like to focus on Linux compatibility for now.

From my own experimentation, it seems like Wayland has some incompatibilities with Electron's/Chromium's desktopCapturer module, but xorg was able to take screenshots without any additional tinkering.

Additionally, some helper functions for determining screen point location are not available cross-platform, so a different way to calculate the screenshot positions/dimensions will be necessary.
See changes here: rDarge@e44e925
and the corresponding scale factor fix here: rDarge@579a13e

Lastly, the window names are slightly different platform-to-platform, so the default window name corresponding to each OS needs to be recognized by the backend to prevent the app from selfdestructing:
rDarge@7f9ee01