add ambience sounds and helper function (#87)

* add ambience sounds and helper function

* minor tweaks

* fix deps

---------

Co-authored-by: BuckarooBanzay <BuckarooBanzay@users.noreply.github.com>

nodes.lua

@@ -537,7 +537,8 @@ for name, def in pairs(nodes) do
 	end
 
 	-- register node
-	minetest.register_node("scifi_nodes:"..name, node_def)
+	local nodename = "scifi_nodes:" .. name
+	minetest.register_node(nodename , node_def)
 
 	-- unified dyes registration
 	if def.colorable and has_unifieddyes_mod then
@@ -574,6 +575,12 @@ for name, def in pairs(nodes) do
 		})
 	end
 
+	if def.ambience then
+		for soundname, opts in pairs(def.ambience) do
+			scifi_nodes.register_ambience(nodename, soundname, opts)
+		end
+	end
+
 	-- advtrains platform registration
 	if has_advtrains_mod and def.advtrains_platform then
 		advtrains.register_platform("scifi_nodes", "scifi_nodes:" .. name)