Add new skills: Double Jump, Ground Pound, Brick Armor, and Brick Shield; implement skill removal signal in SkillManager (#11)

resources/skills/ground_pound_skill.tres

@@ -0,0 +1,23 @@
+[gd_resource type="Resource" script_class="SkillData" load_steps=5 format=3 uid="uid://cseilsspimw1n"]
+
+[ext_resource type="PackedScene" uid="uid://lu3wvpqefekn" path="res://objects/player_skills/ground_pound_skill_component.tscn" id="1_auljr"]
+[ext_resource type="Script" uid="uid://d4crrfmbgxnqf" path="res://scripts/Resources/SkillData.cs" id="1_i1qac"]
+[ext_resource type="Script" uid="uid://dwb0e05pewcsn" path="res://scripts/Resources/SkillUpgrade.cs" id="2_tkhf7"]
+
+[sub_resource type="Resource" id="Resource_upxa7"]
+script = ExtResource("2_tkhf7")
+Cost = 300
+Description = ""
+Properties = Dictionary[String, Variant]({})
+metadata/_custom_type_script = "uid://dwb0e05pewcsn"
+
+[resource]
+script = ExtResource("1_i1qac")
+Name = "GROUND_POUND_SKILL"
+Description = "GROUND_POUND_SKILL_DESCRIPTION"
+IsActive = false
+Level = 1
+Type = 2
+Node = ExtResource("1_auljr")
+Upgrades = [SubResource("Resource_upxa7")]
+metadata/_custom_type_script = "uid://d4crrfmbgxnqf"