At the VS code
press Ctrl+Shift+P
then type Format Document With...
At the end of the list click on Configure Default Formatter...
Now you can choose your favorite beautifier from the list.
Update 2021
if "Format Document With..."
didn't exist any more, go to file
=> preferences
=> settings
then navigate to Extensions
=> Vetur
scroll a little bit then you will see format > defaultFormatter:css
, now you can pick any document formatter that you installed bofer for different file type extensions.