beyond the auto-detected platform download links, add a link to the other platform downloads on filstation.app

[gruns]

currently on filstation.app, the only downloads available is for the platform you're currently on, eg os x. when youre on a mac, the only download links you can see on filstation.app are for os x

additionally to this, add a link below the detected platform downloads to the other platform downloads, too. many popular desktop apps do this, like telegram, discord, slack, firefox, etc

[juliangruber]

Since we don't want to link to the GitHub release page (it's not trivial for all users to figure which release to download), this requires design work by Onda. I think it makes the most sense to collect a few items like this, and then schedule another cycle.