Added building structure

Created harvester building
added harvester particles
added nearest resource func

data/buildings/basic/harvester/harvester.gd

@@ -0,0 +1,20 @@
+extends Building
+
+const CARBON_RESOURCE = preload("res://data/game_resources/carbon/carbon_resource.tres")
+
+func ready(building: BuildingBase) -> void:
+	var nearest_res := Grid.get_nearest_resource(building.position, CARBON_RESOURCE)
+	var _distance = building.position.distance_to(nearest_res)
+	
+	var particles = CPUParticles2D.new()
+	particles.amount = 60
+	particles.spread = 8
+	particles.material = ParticleProcessMaterial.new()
+	particles.radial_accel_max = _distance * -2.5
+	particles.radial_accel_min = _distance * -2.55
+	particles.gravity = Vector2.ZERO
+	particles.direction = building.position.direction_to(nearest_res)
+	particles.initial_velocity_max = _distance * 2.25
+	particles.initial_velocity_min = _distance * 2.2
+	particles.lifetime = 1.65
+	building.add_child(particles)