Use the butler updater tool on Web builds

[PascalLadalle]

If we could adopt the itch.io tool butler, we could offer a build update feature that would:

• spare server bandwidth,
• spare server storage,
• make one liluo link per project (unless user ticks a box to generate a second build, to compare versions or whatnot)
• drastically improve upload times and user experience
• save the planet, most assuredly