Clarify linux icon notes; add note about icon extensions (refs: #125, #128)
Clarify linux icon notes; add note about icon extensions (refs: #125, #128)

Ivshti/electron-packager,Zurico/electron-packager,maxogden/electron-packager,rahatarmanahmed/electron-packager,herrmannplatz/electron-packager,Goobaroo/electron-packager,malept/electron-packager,electron-userland/electron-packager,buddingmonkey/electron-packager,sethlu/electron-packager,electron-userland/electron-packager,Urucas/electron-packager,kvnneff/electron-packager,spinico/electron-packager,plrthink/electron-packager,malept/electron-packager,sethlu/electron-packager,Goobaroo/electron-packager