[webauthn] new commits pushed by vijaybh

The following commits were just pushed by vijaybh to https://github.com/w3c/webauthn:

* Align registries draft and WebAuthn draft and address extension issues (#386)

* Align registries draft and WebAuthn draft and address extension issues

* Correct section references in IANA Considerations section

* Incorporated feedback from Jeff Hodges

* <dfn> markup for reg & authn extension phrases & various cleanups

* Applied [=registration extension=] tag in more places
  by Mike Jones
https://github.com/w3c/webauthn/commit/da9520ab40268541833f64e7436c128edb1aaa62