Part of ACREP-32.

Part of ACREP-32.

Provide new Handlebars helper mkws-best-url, which returns the first
item in a list that matches a regular-expression suggesting that it's
a URL (basically anything that starts with http://, https:// or //).

Also provide mkws-other-urls (not yet tested), which returns all the
other URLs in the list except the first.