Added support for CartoCSS

Code sample was taken from https://github.com/gravitystorm
/openstreetmap-carto/blob/ae990905790a26ae8af107441ce9e85b60ea1266
/amenity-points.mss

lib/linguist/languages.yml

@@ -449,6 +449,14 @@ Cap'n Proto:
   - .capnp
   ace_mode: text
 
+CartoCSS:
+  aliases:
+  - Carto
+  extensions:
+  - .mss
+  ace_mode: text
+  tm_scope: none
+
 Ceylon:
   type: programming
   extensions: