Add a first-view controller and a bunch of things

1. Replace 4k models with low-poly once
2. Use bare mixamo for testing
3. Add a basic menu
4. Add a map with collisions and spawn areas

scenes/utils/menus/choose_side.tscn

@@ -0,0 +1,19 @@
+[gd_scene format=3 uid="uid://cf4pgjll6xhoh"]
+
+[node name="ChooseSide" type="Control"]
+layout_mode = 3
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+
+[node name="Blue" type="Button" parent="."]
+layout_mode = 0
+offset_right = 8.0
+offset_bottom = 8.0
+
+[node name="Red" type="Button" parent="Blue"]
+layout_mode = 0
+offset_right = 8.0
+offset_bottom = 8.0