OptionalNonEmptyCssUrl

Pattern: ^$|^(https?:\/\/)?[a-z0-9]+([-.]+[a-z0-9]+)*\.[a-z]{2,10}([0-9]{1,5})?(\/[^\/]*)*\/[^\/]*\.css$

Example:

{
  "title": "Example",
  "value": "https://website-sample/custom.css"
}