Add support for regex named capture groups

[wankdanker]

This adds support for regex named capture groups (eg: /^(<thing>[^ ]*)/). If there is interest in this and there are changes that need to be made, please let me know, I'm happy to address them.

Example

input:

{ "id" : "prefix-89d4eb62-7d81-11ee-805b-87228db36e11-suffix" }

expression:

{ "uuid": $match(id, /prefix-(?<uuid>[0-9a-z\-]*)-suffix/).namedGroups.uuid }

output:

{ "uuid": "89d4eb62-7d81-11ee-805b-87228db36e11" }