Fix location delegates

- Mark OSMLocationPlugina as singleton in cmake
- Use this plugin for the LocationChooser

src/timeline/LocationComponent.qml

@@ -76,7 +76,7 @@ ColumnLayout {
 
         map.plugin: OsmLocationPlugin.plugin
 
-        LocationMapItem {
+        readonly property LocationMapItem locationMapItem: LocationMapItem {
             latitude: root.latitude
             longitude: root.longitude
             asset: root.asset
@@ -85,6 +85,8 @@ ColumnLayout {
             heading: NaN
         }
 
+        Component.onCompleted: map.addMapItem(locationMapItem)
+
         TapHandler {
             acceptedButtons: Qt.LeftButton
             onTapped: {