Add note array and view.

rhythm_game/note/lane_view.gd

@@ -0,0 +1,21 @@
+## A NoteView that stores notes that exist on a lane.
+class_name LaneView extends NoteView
+
+## The lane notes will be filtered by.
+@export var lane: int
+
+## Get the array this LaneView refers to.
+func get_data() -> NoteSubset:
+	return _lane_notes
+
+func update_current_beat(beat: float) -> void:
+	_current_beat = beat
+	_update_view_relative_to_notes(_lane_notes)
+
+# ======== Implementation ======== #
+var _lane_notes: NoteSubset
+
+func _set_data(p_notes: NoteArray) -> void:
+	notes = p_notes
+	_lane_notes = NoteSubset.get_notes_in_lane(p_notes, lane)
+	_reset_view()