Add an implementation skeleton for Ed25519 and X25519 in WebCrypto.

Curve25519 is introduced behind the feature flag WebCryptoCurve25519.

Bug: 1032821
Change-Id: I6051eca2027ecbcfd2236853aa4f691366802601
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1958596
Reviewed-by: Kentaro Hara <[email protected]>
Reviewed-by: Eric Roman <[email protected]>
Commit-Queue: Qingsi Wang <[email protected]>
Cr-Commit-Position: refs/heads/master@{#745323}
15 files changed