Added basic projectile

Changelog:
1. Linear projectile scene and script
2. project.godot 3D collision layers renamed

base/scripts/projectiles/linear_projectile.gd

@@ -0,0 +1,23 @@
+extends Area3D
+
+## Speed of the projectile in meters per second
+@export_range(0,1000,0.01,"or_greater","suffix:m/s") var speed : float
+## Damage of projectile
+@export var damage : float
+
+func _ready() -> void:
+	body_entered.connect(on_body_entered)
+
+## Invoked when area contacts collision object
+func on_body_entered(body : Node):
+	if body.is_in_group("Entities") == false:
+		return
+	
+	# Owner needs to be set to Entity node when spawning projectile
+	if owner is Entity:
+		body.get_node("Entity").deal_damage(damage,owner)
+	else:
+		body.get_node("Entity").deal_damage(damage,null)
+
+func _physics_process(delta: float) -> void:
+	global_position += global_transform.basis.z * delta