Add Staff of Light sound

(It sounds better than reusing the portal ignition sound)

README.md

@@ -55,6 +55,7 @@ SOFTWARE.
 
 ### [Attribution 3.0 Unported (CC BY 3.0)](https://creativecommons.org/licenses/by/3.0/)
 
+ * `nether_lightstaff.ogg` is "Fire Burst" by [SilverIllusionist](https://freesound.org/people/SilverIllusionist/), 2019
  * `nether_portal_ambient.ogg` & `nether_portal_ambient.0.ogg` are extractions from "Deep Cinematic Rumble Stereo" by [Patrick Lieberkind](http://www.lieberkindvisuals.dk), used under CC BY 3.0
  * `nether_portal_extinguish.ogg` is an extraction from "Tight Laser Weapon Hit Scifi" by [damjancd](https://freesound.org/people/damjancd), used under CC BY 3.0
  * `nether_portal_ignite.ogg` is a derivative of "Flame Ignition" by [hykenfreak](https://freesound.org/people/hykenfreak), used under CC BY 3.0. "Nether Portal ignite" is licensed under CC BY 3.0 by Treer.

tools.lua

@@ -268,8 +268,7 @@ local function lightstaff_on_use(user, boltColorString, lightDuration)
 	aimPos.y = aimPos.y + (distance / nether.lightstaff_velocity) * nether.lightstaff_gravity
 	local boltDir = vector.normalize(vector.subtract(aimPos, wieldPos))
 
-	-- needs a proper casting sound, instead of the portal ignition
-	minetest.sound_play("nether_portal_ignite", {to_player = playerName, gain = .3, pitch = 1.7}, true)
+	minetest.sound_play("nether_lightstaff", {to_player = playerName, gain = 0.8}, true)
 
 	-- animate a "magic bolt" from wieldPos to aimPos
 	local particleSpawnDef = {