game: add bullet and impacts

game/bullet_decal_smoke.gdshader

@@ -0,0 +1,14 @@
+shader_type spatial;
+
+void vertex() {
+	// Called for every vertex the material is visible on.
+}
+
+void fragment() {
+	// Called for every pixel the material is visible on.
+}
+
+//void light() {
+//	// Called for every pixel for every light affecting the material.
+//	// Uncomment to replace the default light processing function with this one.
+//}