refactor: improve device interface types (#996)

app/assets/javascripts/Device/StartApplication.ts

@@ -0,0 +1,8 @@
+import { WebOrDesktopDevice } from './WebOrDesktopDevice'
+
+export type StartApplication = (
+  defaultSyncServerHost: string,
+  device: WebOrDesktopDevice,
+  enableUnfinishedFeatures: boolean,
+  webSocketUrl: string,
+) => Promise<void>