Added Coin Sparkle Effects (#350)

* Just the Coin Sparkle stuff

FYI, if a property in the json is formatted like `exa.exb` then it reads `exa` as another object and `exb` as a property in `exa` assuming the root `property_node` contains this object.
Also primarily for Resource Packs to change how the particles work and should explain how I got there with my personal SMAS skin.

* Added Coin Sparkle Texture to Scene

Of course I broke it in some form.

Assets/Sprites/Items/Coin.json

@@ -85,6 +85,9 @@
 			"loop": true
 		}
 	},
+	"properties": {
+		"can_spawn_particles": true
+	},
 	"variations": {
 		"default": {"source": "StaticCoin.png", "rect": [0, 0, 64, 16]},
 		"Underground": {"source": "StaticCoin.png", "rect": [0, 16, 64, 16]},

Assets/Sprites/Items/SpinningCoin.json

@@ -31,6 +31,9 @@
 			"loop": true
 		}
 	},
+	"properties": {
+		"can_spawn_particles": true
+	},
 	"variations": {
 		"default": {
 			"source": "SpinningCoin.png",

Assets/Sprites/Particles/CoinSparkle.json

@@ -0,0 +1,10 @@
+{
+	"properties": {
+		"amount": 3,
+		"process_material.emission_shape": 1,
+		"material.particles_anim_h_frames": 8
+	},
+	"variations": {
+		"default": {"source": "CoinSparkle.png", "rect": [0, 0, 64, 8]}
+	}
+}