Specgo
Specgo is a command-line utility for opening web specifications (such as those from the WHATWG, W3C, or IETF) in your web browser.
Once you install it, using
npm install -g specgo
you can use it like so:
specgo html # opens https://html.spec.whatwg.org/multipage/
specgo mix # opens https://w3c.github.io/webappsec-mixed-content/
specgo mixed-content # ditto
specgo rfc7234 # opens https://httpwg.org/specs/rfc7234.html