[w3c/webauthn] db1a3a: Update index.bs

  Branch: refs/heads/balfanz-patch-4
  Home:   https://github.com/w3c/webauthn
  Commit: db1a3a520cb59ae21aa48564bbba59338ae4c8b2
      https://github.com/w3c/webauthn/commit/db1a3a520cb59ae21aa48564bbba59338ae4c8b2
  Author: balfanz <dirk@balfanz.net>
  Date:   2017-10-11 (Wed, 11 Oct 2017)

  Changed paths:
    M index.bs

  Log Message:
  -----------
  Update index.bs