feat+fix: allow forwarding extra info to InstanceImportTask

This allows us to pass to the creation instances their actual pack ID
and version ID, that in Flame's case, are only available before starting
to create an instance.

Signed-off-by: flow <flowlnlnln@gmail.com>

launcher/ui/pages/modplatform/flame/FlamePage.h

@@ -99,5 +99,5 @@ private:
     Flame::ListModel* listModel = nullptr;
     Flame::IndexedPack current;
 
-    QString selectedVersion;
+    int m_selected_version_index = -1;
 };