This allows users to update the icons on Windows computers as well. Requires at least Windows 7. The update mechanic works the same as in update.sh, but with the tweaks of #37 to recognize a custom icons.json (https://github.com/brianegan/font_awesome_flutter/pull/37/commits/dd08ea2e5ff2812fe5a5569d33936ce14a518c15) already in there.