More consistent library list view padding (closes #3509)

app/src/main/res/layout/source_list_item.xml

@@ -6,6 +6,8 @@
     android:layout_height="@dimen/material_component_lists_single_line_with_avatar_height"
     android:layout_gravity="center_vertical"
     android:background="@drawable/list_item_selector"
+    android:paddingStart="8dp"
+    android:paddingEnd="8dp"
     tools:layout_editor_absoluteX="0dp"
     tools:layout_editor_absoluteY="25dp">