[Android/iOS] Smartwatch support

[tobiasKaminsky]

Initial version should only contain notifications of Nextcloud server, e.g. when there is an announcement, somebody shares a file.

• companion app of already installed app on mobile
• show (push) notification (same as on app) on watch
• possible to show primary action, secondary action or list of other options
• possible to react on those

This issue is "just" for research and rough estimation how much time this costs. @thisIsTheFoxe @tobiasKaminsky

[thisIsTheFoxe]

Is this related to nextcloud/iOS#1702? Because iOS "User[facing] Notifications" are automatically relayed to the watch without the need for a companion app. But if you mean a separate app that basically only has one screen i.e. a list of notifications.. I'd say about a week. We can't reuse any views because of WatchKit limitations. And the second challenge is app-to-watch communication and if we can easily add the communication library (which will also need some further adjustments). Also, SwiftyXMLParser has a deployment target of watchOS 6.