Add new isPasskeyPlatformAuthenticatorAvailable()

[MasterKale]

Describe the issue

w3c/webauthn#1901 is adding a new PublicKeyCredential.isPasskeyPlatformAuthenticatorAvailable() to offer RP's a signal that users will likely be able to use a passkey via the local platform authenticator, or via hybrid authentication.

Reproduction Steps

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Expected behavior

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Code Samples + WebAuthn Options and Responses

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Dependencies

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SimpleWebAuthn Libraries

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Additional context

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[MasterKale]

Update: this method is being removed from WebAuthn in w3c/webauthn#1936, but there's no reason I couldn't still add a method of this name to this project using the proposed getClientCapabilities() API that's being proposed in w3c/webauthn#1923.

[bschoenmaeckers]

Is the return value going to be undefined when passkeyPlatformAuthenticator is not present in getClientCapabilities()?