[w3c/webauthn] 40875f: use the registered ext ids in examples

  Branch: refs/heads/consistent-extension-ids-588
  Home:   https://github.com/w3c/webauthn
  Commit: 40875f1e798bac1cd7f6393c16da39d671e32ebb
      https://github.com/w3c/webauthn/commit/40875f1e798bac1cd7f6393c16da39d671e32ebb
  Author: rlin1 <rolf@noknok.com>
  Date:   2017-11-09 (Thu, 09 Nov 2017)

  Changed paths:
    M index.bs

  Log Message:
  -----------
  use the registered ext ids in examples