Create an app updater system

[stackotter]

Swift Bundler is well placed to vend an app updater system.

I'll flesh out some more details at some point, but we could have a publish subcommand that can (in addition to targeting app stores) produce update manifest files that devs can either host or get us to host, and then point their app's updater at it to check for and install updates. We would also vend a library product that people can use to handle updates.

import Updater

...

if let update = Updater.checkForUpdate(/* manifest URL */) {
    // How devs handle updates would depend on the UI framework they use.
    // Our updater framework would probably provide a SwiftCrossUI-based
    // updater UI by default, and maybe a CLI-based updater UI too. The updater
    // UI's would probably be in seperate products so that devs can just import
    // the ones they need.
}

This could eventually be expanded to a service where we host built apps on behalf of devs, but that would be further down the line.