Add client extensions to getClientCapabilities() per WebAuthn L3 spec
https://w3c.github.io/webauthn/#sctn-getClientCapabilities
Fixed: 377366929
Change-Id: I954430fa786a9350c463a004c569d69d1e66ef73
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5999316
Commit-Queue: Andrii Natiahlyi natiahlyi@google.com
Reviewed-by: Adam Langley agl@chromium.org
Cr-Commit-Position: refs/heads/main@{#1379271}