Add a contact form matcher

I have read through the issue at #2769191: Invalid condition operator when matching against Config Entities., and I see that contact forms are not available as a matcher

But my client needs to be able to easily add links to several contact forms, and does not use the personal contact form. We are likely to ajaxify these links in a modal popup, so solutions like creating content entities and adding contact forms to those just so we can link to them are not very appropriate.

So this is a combination feature request / support request to add a specific matcher for contact forms. A few nudges in the right direction would be appreciated, thanks.