Show icon previews in icon pickers

Sidebar.py

@@ -296,7 +296,11 @@ class Sidebar(ft.Container):
             value=Bookmark.Icon,
             label="Icon",
             options=[
-                ft.DropdownOption(key=Name, text=IconLabelOverrides.get(Name, Name.split("_")[0].title()))
+                ft.DropdownOption(
+                    key=Name,
+                    text=IconLabelOverrides.get(Name, Name.split("_")[0].title()),
+                    leading_icon=getattr(ft.Icons, Name),
+                )
                 for Name in IconChoices
             ],
         )