Capture events in callbacks

Using dedicated callbacks increase code modularity, which is good.

Player.gd

@@ -53,12 +53,12 @@ func _ready():
 
 	tween.connect_into(self)
 
-func _physics_process(_d):
-	# TODO : use action callbacks
-	if Input.is_action_just_pressed(turn_left_action):
-		dire_delta = -1
-	elif Input.is_action_just_pressed(turn_right_action):
-		dire_delta = 1
+func _unhandled_input(event):
+	if event.is_pressed():
+		if event.is_action(turn_left_action):
+			dire_delta = -1
+		elif event.is_action(turn_right_action):
+			dire_delta = 1
 
 func _on_game_start():
 	move()