Also add script for generating the PNGs and add pre-rendered PNGs for the Linux electron build which means you don't need icns2png to build it and the Linux icons are straight from the SVG rather than resized bitmaps.
Missed from https://github.com/vector-im/vector-web/pull/2551 * squirrel hooks file for handling install / uninstall events * Install 'spinner' gif for windows (ours does not spin)
From https://github.com/vector-im/vector-web/pull/2511 but with just the actual electron changes
