The URLs of the form `help://man/<section>/<page>` link to another help
page inside the help application. All previous relative page links are
replaced by this new form. This doesn't change any behavior but it looks
much nicer :^)
Note that man doesn't handle these new links, but the previous relative
links didn't work either.
Through links in the help page, the user can directly launch the app
whose help page is currently viewed. The idea for this feature came up
in the discussion of #11557
(https://github.com/SerenityOS/serenity/pull/11557#issuecomment-1004830728
). The intention is that the user can simply open the app they are
currently trying to understand, and play around with it, learn by doing,
or follow along with any guide that may be present in the help page. It
feels very great :^)
