[w3c/webauthn] af8b20: add JSON explicit parsing step

  Branch: refs/heads/jeffh-fix-792-use-utf-8-decode-directly
  Home:   https://github.com/w3c/webauthn
  Commit: af8b20b7df1caf81b4a5247b845ab15e531e4782
      https://github.com/w3c/webauthn/commit/af8b20b7df1caf81b4a5247b845ab15e531e4782
  Author: JeffH <Jeff.Hodges@PayPal.com>
  Date:   2018-02-09 (Fri, 09 Feb 2018)

  Changed paths:
    M index.bs

  Log Message:
  -----------
  add JSON explicit parsing step