feat: 增加欢迎板

- 增加欢迎板场景
- 增加与玩家的交互，点击E弹出弹出框

scenes/ui/welcome_dialog.tscn

@@ -0,0 +1,117 @@
+[gd_scene load_steps=5 format=3 uid="uid://d8mam0n1a3b5"]
+
+[ext_resource type="Script" uid="uid://cu6x4dxhsylw2" path="res://scenes/ui/WelcomeDialog.gd" id="1_vs5b1"]
+[ext_resource type="Texture2D" uid="uid://v7loa3smfkrd" path="res://assets/materials/WelcomeBoard.png" id="2_dy5hw"]
+
+[sub_resource type="StyleBoxFlat" id="StyleBoxFlat_card"]
+bg_color = Color(1, 1, 1, 1)
+corner_radius_top_left = 10
+corner_radius_top_right = 10
+corner_radius_bottom_right = 10
+corner_radius_bottom_left = 10
+shadow_color = Color(0, 0, 0, 0.2)
+shadow_size = 10
+
+[sub_resource type="StyleBoxFlat" id="StyleBoxFlat_btn_rounded"]
+bg_color = Color(0.95, 0.95, 0.95, 1)
+border_width_left = 1
+border_width_top = 1
+border_width_right = 1
+border_width_bottom = 1
+corner_radius_top_left = 20
+corner_radius_top_right = 20
+corner_radius_bottom_right = 20
+corner_radius_bottom_left = 20
+
+[node name="WelcomeDialog" type="CanvasLayer"]
+script = ExtResource("1_vs5b1")
+
+[node name="ColorRect" type="ColorRect" parent="."]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+color = Color(0, 0, 0, 0.4)
+
+[node name="CenterContainer" type="CenterContainer" parent="."]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+
+[node name="PanelContainer" type="PanelContainer" parent="CenterContainer"]
+custom_minimum_size = Vector2(400, 350)
+layout_mode = 2
+theme_override_styles/panel = SubResource("StyleBoxFlat_card")
+
+[node name="VBoxContainer" type="VBoxContainer" parent="CenterContainer/PanelContainer"]
+layout_mode = 2
+theme_override_constants/separation = 10
+
+[node name="Header" type="HBoxContainer" parent="CenterContainer/PanelContainer/VBoxContainer"]
+layout_mode = 2
+alignment = 1
+
+[node name="Spacer" type="Control" parent="CenterContainer/PanelContainer/VBoxContainer/Header"]
+layout_mode = 2
+size_flags_horizontal = 3
+
+[node name="Title" type="Label" parent="CenterContainer/PanelContainer/VBoxContainer/Header"]
+layout_mode = 2
+theme_override_colors/font_color = Color(0, 0, 0, 1)
+theme_override_font_sizes/font_size = 18
+text = "欢迎来到 Datawhale Town!"
+
+[node name="Spacer2" type="Control" parent="CenterContainer/PanelContainer/VBoxContainer/Header"]
+layout_mode = 2
+size_flags_horizontal = 3
+
+[node name="CloseButton" type="Button" parent="CenterContainer/PanelContainer/VBoxContainer/Header"]
+custom_minimum_size = Vector2(30, 30)
+layout_mode = 2
+text = "X"
+flat = true
+
+[node name="HSeparator" type="HSeparator" parent="CenterContainer/PanelContainer/VBoxContainer"]
+layout_mode = 2
+
+[node name="LogoContainer" type="CenterContainer" parent="CenterContainer/PanelContainer/VBoxContainer"]
+layout_mode = 2
+
+[node name="TextureRect" type="TextureRect" parent="CenterContainer/PanelContainer/VBoxContainer/LogoContainer"]
+custom_minimum_size = Vector2(300, 100)
+layout_mode = 2
+texture = ExtResource("2_dy5hw")
+expand_mode = 1
+stretch_mode = 5
+
+[node name="BodyText" type="Label" parent="CenterContainer/PanelContainer/VBoxContainer"]
+layout_mode = 2
+theme_override_colors/font_color = Color(0.3, 0.3, 0.3, 1)
+theme_override_font_sizes/font_size = 14
+text = "连接·共生·见证
+Datawhale Town —— 学习者的赛博家园与精神坐标。
+✨ 实时广场：看大家都在学什么。
+🏠 个人空间：展示你的学习笔记与作品。
+🤝 开源营地：更有氛围的组队学习体验。"
+horizontal_alignment = 1
+autowrap_mode = 3
+
+[node name="Spacer3" type="Control" parent="CenterContainer/PanelContainer/VBoxContainer"]
+layout_mode = 2
+size_flags_vertical = 3
+
+[node name="ActionContainer" type="CenterContainer" parent="CenterContainer/PanelContainer/VBoxContainer"]
+layout_mode = 2
+
+[node name="StartButton" type="Button" parent="CenterContainer/PanelContainer/VBoxContainer/ActionContainer"]
+custom_minimum_size = Vector2(150, 40)
+layout_mode = 2
+theme_override_colors/font_color = Color(0, 0, 0, 1)
+theme_override_styles/normal = SubResource("StyleBoxFlat_btn_rounded")
+text = "开始探索"
+
+[node name="MarginContainer" type="MarginContainer" parent="CenterContainer/PanelContainer/VBoxContainer"]
+layout_mode = 2