Add Compression Transport Dictionary support

[tunetheweb]

Fixes #7186

The BCD data has already been merged in https://github.com/mdn/browser-compat-data/pull/26257 but since that is a collection of HTTP headers and attributes I'm adding this separate PR for the overall feature.

The Draft Spec has been submitted for approval and should have an RFC in next few months. Happy to update this when it does.