Add workspace-prefixed URL scheme for Whimsical (#860)

Whimsical URLs can include a workspace name prefix, e.g.
https://whimsical.com/workspace-name/board-title-AbCdEfGh

The existing scheme `https://whimsical.com/*` only matches
single-segment paths. This adds `https://whimsical.com/*/*`
to match workspace-prefixed URLs, which the Whimsical oEmbed
endpoint already supports.

Author: armincerf

providers/whimsical.yml

@@ -4,6 +4,7 @@
   endpoints:
     - schemes:
         - https://whimsical.com/*
+        - https://whimsical.com/*/*
       url: https://whimsical.com/api/oembed
       example_urls:
         - https://whimsical.com/api/oembed?url=https%3A%2F%2Fwhimsical.com%2Fhow-oembed-works-7wvH66hEVUugCDkpPDbcuc&format=json