feat(ui): draw pane frames, page keys and a scroll thumb

beefy_player/widgets/help.py

@@ -21,6 +21,7 @@ if TYPE_CHECKING:
 
 HELP_ROWS: tuple[tuple[str, str], ...] = (
     ("↑ / ↓  j / k", "move through the station list"),
+    ("pgup / pgdn", "page through the station list"),
     ("enter", "tune in to the selected station"),
     ("space", "play / pause the current station"),
     ("s", "stop playback"),