feat: started work on save system

WIP - build doesn't work yet

src/UI/main_panel/date_marker.gd

@@ -0,0 +1,12 @@
+class_name DateMarker extends HBoxContainer
+
+@export var date_text_label: RichTextLabel
+
+# Called when the node enters the scene tree for the first time.
+func _ready() -> void:
+	pass # Replace with function body.
+
+
+# Called every frame. 'delta' is the elapsed time since the previous frame.
+func _process(delta: float) -> void:
+	pass