I am trying to output a field as a custom link using the rewrite configuration with Twig replacement patterns in Drupal 8 Views, as depicted in the screenshot below.

Views field: (W)here is New York?
 Desired output: example.com/posts/where-is-new-york

In the Views field configuration, I have selected:

Rewrite results: Output this field as a custom link

and entered a few different regex patterns, to no avail. The result I get is always:

example.com/posts/%28w%29here%20is%20new%20york

Is there a third-party plugin for PCRE-style regex filters for Drupal 8? Or is this something that must be handled in a template file, i.e. views-view-field.html.twig?