Tauri improvements

Summerized changes: The following changes: - `path_trav` had to be removed - path traversal is prevented by not allowing certain characters in the filename - `path_trav` uses `fs::canonicalize` internally, which always fails if a file does not exist => not suited for our needs - tauri notification replaced with `mac-notification-sys` - this has the advantage of further modification to allow the user to reply on messages directly in the notification - file download supports progress - a callback can be registered when starting the download (see below) - set badge count is supported by `setBadgeCount(count: number)` - app needs to be packaged for this to work - `this.__isApp = !this.__isBrowser` was replaced with `this.__isApp = window.__TAURI__ !== undefined` - the old version was not working ```js await UtilitiesRuntime.requestFileDownload( event.file.url, event.file.name, (current, total) => console.log(`${Math.round(current/total*100)}% done`) ); ``` - https://github.com/prose-im/prose-app-web/pull/66/commits/a57ed39ce41615466963a2719cfc1f1ec647c0d0 adds support for deep linking. If the application is compiled and placed in the `/Applications` folder, Prose registers as a opener for `xmpp://` URLs