feat: maintain scroll position in vocab/morph analytics view (#1791)

Author: ggurdin

lib/pangea/analytics_details_popup/morph_analytics_view.dart

@@ -33,6 +33,7 @@ class MorphAnalyticsView extends StatelessWidget {
 
             return snapshot.connectionState == ConnectionState.done
                 ? ListView.builder(
+                    key: const PageStorageKey<String>('morph-analytics'),
                     itemCount: morphs.displayFeatures.length,
                     itemBuilder: (context, index) => morphs
                             .displayFeatures[index].displayTags.isNotEmpty

lib/pangea/analytics_details_popup/vocab_analytics_view.dart

@@ -82,6 +82,7 @@ class VocabAnalyticsView extends StatelessWidget {
     return Padding(
       padding: const EdgeInsets.symmetric(vertical: 20),
       child: ListView(
+        key: const PageStorageKey<String>('vocab-analytics'),
         children: [flowers, greens, seeds],
       ),
     );