Allow opening locations in your preferred map

Once someone shares a location with you, typically you want to open it in your preferred mapping application or website. For example, being sent a location to a restaurant and needing to route it via Google Maps.

Now in NeoChat you can click on the "Open Externally" button on a location message. On KDE Plasma, the default application can be set under System Settings. On Android, this URI is handled by Google Maps and possibly others.