Add support for Windows 10 WebAuthn API

[micolous]

This adds support for Windows 10's WebAuthn API. This is effectively mandatory on Windows 10 Build 1903 and later, as it blocks direct access to FIDO authenticators for non-Administrator users.

webauthn2.mp4

This also adds a new authenticate example, pulled from SoftToken's unit tests.

Tasks remaining:

• Finish populating WEBAUTHN_AUTHENTICATOR_MAKE_CREDENTIAL_OPTIONS
• Implement perform_auth
• Come up with a reliable way to get/pass the HWND for the application window
• Find a way to pass in application info
• There's probably lifetime issues here, lots of raw pointers... Microsoft's windows crate has a very unsafe API
• Make new test program for making test credentials (rather than stomping nfc_token_info...
• Remove println! debugging
• Set up CI on Windows (Run CI on windows #212)
• Split all the non-Windows changes out of this PR (Add common fields from win10 branch #211 Remove support for credBlob, per #206 #210)

Fixes #

• cargo fmt has been run
• cargo test has been run and passes
• documentation has been updated with relevant examples (if relevant)

[Firstyear]

What else would you want before we merge this?

[micolous]

What else would you want before we merge this?

Once #212 is in, I'll need to rebase this and it should be good to go.