lua: icecast: fix indent and add source meta

share/lua/sd/icecast.lua

@@ -44,6 +44,7 @@ function main()
                           genre=station.children_map["genre"][1].children[1],
                           nowplaying=station.children_map["current_song"][1].children[1],
                           meta={
+                                  ["Listing Source"]="dir.xiph.org",
                                   ["Icecast Bitrate"]=station.children_map["bitrate"][1].children[1],
                                   ["Icecast Server Type"]=station.children_map["server_type"][1].children[1]
                           }} )