Add 'ங்க' as a secondary transliteration of 'nga'

This allows varnam to learn that 'kurangu' corresponds to 'குரங்கு
', and not 'குரஙு
', for instance

Author: Kishore96in

schemes/ta

@@ -55,7 +55,8 @@ consonants ["ka", "qa", "ga", ["ha"]] => "க",
 		      ["fa"] => "ஃப"
 
 
-consonants ["kk*"] => ["க#{$virama}க#{$virama}*1"]
+consonants ["kk*"] => ["க#{$virama}க#{$virama}*1"],
+			[["nga"]] =>  "ங#{$virama}க"
 
 infer_dead_consonants false