Move remaining code to app module

There's still some stuff that could potentially go elsewhere but I think it's enough for now.

src/app/qml/OsmLocationPlugin.qml

@@ -0,0 +1,24 @@
+// SPDX-FileCopyrightText: 2021 Tobias Fella <fella@posteo.de>
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+pragma Singleton
+
+import QtQuick
+import QtLocation
+
+QtObject {
+    id: root
+
+    property string userAgent: Application.name + "/" + Application.version + " (kde-devel@kde.org)"
+    property var plugin: Plugin {
+        name: "osm"
+        PluginParameter {
+            name: "osm.useragent"
+            value: root.userAgent
+        }
+        PluginParameter {
+            name: "osm.mapping.providersrepository.address"
+            value: "https://autoconfig.kde.org/qtlocation/"
+        }
+    }
+}