title: how to add extra css to a fabricjs text object?
body: <p>when using fabricjs textbox, I'd like to add extra css to textbox so that the edit area is more beabutiful. 
  The effect would be like this.
  <a href="https://www.w3schools.com/CSSref/tryit.asp?filename=trycss3_border-image" rel="nofollow noreferrer">https://www.w3schools.com/CSSref/tryit.asp?filename=trycss3_border-image</a></p>
  
  <p>Anyone knows how to implement this? </p>
  
  <p>Thank you so much.</p>