Add custom content patterns.

[kyle-winkelman]

Demonstrate how users can create ContentPatternExtensions for extending WireMock's matching abilities.

References

• Support custom content patterns and rework content pattern deserialization. wiremock#2592

Submitter checklist

• The PR request is well described and justified, including the body and the references
• The PR title represents the desired changelog entry
• If the change against WireMock 2 functionality (incompatible with WireMock 3),
  it is submitted against the 2.x branch
• The repository's code style is followed (see the contributing guide)

Details: Contributor Guide

[oleg-nenashev]

The content itself looks good to me, but a redirect is needed.
P.S: I am no longer a maintainer of this repo, just passing by

[oleg-nenashev]

If implemented as is, it breaks the original page access. At least a redirect is needed in the markdown file

[leeturner]

This all looks fine. @oleg-nenashev is correct about the redirect though. Changing the name of the file will change the url structure so all the indexed pages in the search engines will return a 404. If you take a look at the other pages on the site, some of them have a redirect_from element in the front matter. This is what we need here