[webauthn] new commits pushed by vijaybh

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

* IDL cleanup: don't require callers to create Credential objects

This is the minimal version of the change required to fix the IDL 
issue
that @jcjones brought up regarding Credential objects. Unlike PR #158,
it retains the credential type and leaves the actual API surface and
samples unchanged.

If we pick this approach, PR #158 can be closed out and will no longer
be necessary.
  by Vijay Bharadwaj
https://github.com/w3c/webauthn/commit/c79e21b6ad5804e84bbee4983706366455000494

* Merge pull request #159 from w3c/vgb-credentialObjectKeep

IDL cleanup: don't require callers to create Credential objects
  by J.C. Jones
https://github.com/w3c/webauthn/commit/2b72ddfb805a4a0e2797afccea88cfb504fc195e

* Merge remote-tracking branch 'refs/remotes/origin/master' into 
vgb-modular-attestation
  by Vijay Bharadwaj
https://github.com/w3c/webauthn/commit/c27b4bfb3e9c3643adccbd734b5048130b37080e