Add support for Qt Designer

[crewshin]

Describe the solution you'd like
Qt includes an application called Designer that lets you build interfaces graphically a lot like Interface Builder in Xcode. More info available here: https://doc.qt.io/qtcreator/creator-using-qt-quick-designer.html

Describe alternatives you've considered
None. This is a native Qt solution.

Additional context
Designer saves .ui files that can be imported and used from within supported platforms. PyQt is a great example of this in action.

[crewshin]

This is slightly different but might be useful for reference. I built this a long time ago with Qt (cpp), but I'd imagine the .ui file should be the same.

https://github.com/crewshin/KickAssGUI <-- silly name was a play on words from the binaries it used. Renderer was called Arnold. kick was the renderer and .ass were the files it used to render. And well, it was a GUI.

[SantiiRepair]

What happened?