Add command to open ~/.atom/user.less in an editor

src/workspace.coffee

@@ -38,6 +38,10 @@ class Workspace extends Model
     paneContainer: @paneContainer.serialize()
     fullScreen: atom.isFullScreen()
 
+  # Private: Open ~/.atom/user.less or ~/.atom.user.css
+  openUserStylesheet: ->
+    @open(atom.themes.getUserStylesheetPath())
+
   # Public: Asynchronously opens a given a filepath in Atom.
   #
   # * filePath: A file path