[w3c/webauthn] b84d9c: Emphasise that the CollectedClientData can be exte...

  Branch: refs/heads/master
  Home:   https://github.com/w3c/webauthn
  Commit: b84d9cb9dd1fb80ac000de0bf3e92e92338eb357
      https://github.com/w3c/webauthn/commit/b84d9cb9dd1fb80ac000de0bf3e92e92338eb357
  Author: Adam Langley <agl@imperialviolet.org>
  Date:   2018-04-11 (Wed, 11 Apr 2018)

  Changed paths:
    M index.bs

  Log Message:
  -----------
  Emphasise that the CollectedClientData can be extended. (#827)

* Emphasise that the CollectedClientData can be extended.

There is a risk that RPs will implement overly simplistic parsing of the
CollectedClientData and end up intolerant of any future additions. This
change emphasises the need to parse it properly and will be coupled with
a behaviour in Chrome that inserts a key (`new_keys_may_be_added_here`)
in a random 20% of cases.

* Make the note a "Note:"