Support returning extension outputs

While preparing #21, I discovered that browser wasn’t actually returning extension results due to some weird issue with navigator.credentials.create()/get() returning a credential with non-enumerable properties, so the spread operator was ineffective.

Anyway after some more digging it turns out that TypeScript’s AuthenticationExtensionsClientInputs and AuthenticationExtensionsClientOutputs definitions are wildly out of date, especially due to a recent WebAuthn spec change that removed a bunch of outdated extensions. Therefore I need to upgrade browser to support returning the results of getClientExtensionResults() to support the list of extension currently defined in the spec:

• appid
• appidExclude
• uvm
• credProps

[MasterKale]

@Moumouls PR #94 just landed and has been published as v2.1.0. @simplewebauthn/browser@2.1.0 will now return back the value of credential.getClientExtensionResults() as the new clientExtensionResults property on the values that are returned by both startAttestation() and startAssertion().

[MasterKale]

Extension support is only partially functional. generateAttestationOptions() and generateAssertionOptions() accept an extensions argument that gets passed straight through to the returned object without manipulation. There shouldn’t be any issues with passing extensions to authenticators, including txAuthSimple and txAuthGeneric (which I think are now officially deprecated, for what it’s worth?).

Where things fall down is getting the resulting extension output back to the RP so that they can be used. @simplewebauthn/browser still needs to be updated to return the return value from getClientExtensionResults().