Add a way to make the view follow a marker
In GNOME Maps, there's an open issue to make the map view follow the user's current location: gnome-maps#201. I tried implementing it, but it proved difficult because Maps doesn't have easy access to information about why the map is being moved. It may be much easier to solve this problem in libchamplain.
What would probably help is to have a ChamplainView:follow-marker
property. If it's null, the map view works as normal. If it's a ChamplainMarker, the map view stays centered on that marker until it's moved for another reason. Zooming using the scroll wheel would be centered on the marker rather than on the cursor location.