Add skill management system with unlocker and save functionality

scripts/game_manager.gd

@@ -4,6 +4,7 @@ extends Node
 var player_state = {
 					   "coins": 0,
 					   "lives": 3,
+					   "unlocked_skills": [],
 				   }
 
 
@@ -36,4 +37,18 @@ func set_lives(amount: int) -> void:
 
 
 func get_lives() -> int:
-	return player_state["lives"]
+	return player_state["lives"]
+
+
+func is_skill_unlocked(skill_name: String) -> bool:
+	return skill_name in player_state["unlocked_skills"]
+
+
+func unlock_skill(skill_name: String) -> void:
+	if not is_skill_unlocked(skill_name):
+		player_state["unlocked_skills"].append(skill_name)
+
+
+func unlock_skills(skill_names: Array[String]) -> void:
+	for skill_name in skill_names:
+		unlock_skill(skill_name)