Consider switching to NSIS

[Stanzilla]

I will use this issue to track what would be needed to transition our Windows installer from using Squirrel to NSIS.

NSIS is the recommended and most supported target on Windows. It replaced Squirrel as the default target a while ago. Squirrel.Windows usage is actually deprecated

See electron-userland/electron-builder#837 which also includes good info on how to handle the transition properly.

It would fix:

• Update prompt links to json instead of GitHub releases #2621

It would add the ability to run scripts after the installer is done, which we could use to fix #2823

It would add some features we often denied, like being able to remove user settings after uninstall

[LabhanshAgrawal]

we're using nsis now