Merge pull request #3769 from Maxhodges/keymap-advice

Warn new users we are using a little known format (cson), not the more popular json doc notation.

dot-atom/keymap.cson

@@ -19,3 +19,5 @@
 # You can find more information about keymaps in these guides:
 # * https://atom.io/docs/latest/customizing-atom#customizing-key-bindings
 # * https://atom.io/docs/latest/advanced/keymaps
+#
+# Bindings not working? Be aware that cson follows CoffeeScript notation with differs from json.