Documentation of header validation

Is there documentation for the header validation feature that is mentioned in the readme? The link there is pointing to https://cloudflare.github.io/itty-router-openapi/user-guide/header-parameters/ but unfortunately that page is not currently present.

Start by checking the README reference to header validation and the documentation site path at cloudflare.github.io/itty-router-openapi/user-guide/header-parameters/. Confirm where the related guide belongs and what the feature supports. Done means the header validation documentation is available and the README link resolves to it.

Written by the indexing model from the issue text.