UiAvatar Field - add randomColor() or allow customization of url

[mrvnklm]

Issue
When using UiAvatar Field I think one of the most important features is random color, which there is no possiblity to use with the field provided by Nova.

Possible solution
Add randomColor() method to set &random=true in URL or even allow extendURL($string) to be able to extend the URL with custom params