NotSupportedError when using NODE-ED25519 keys

[yusefnapora]

When calling crypto.subtle.importKey or crypto.subtle.generateKey with an algorithm of { name: 'NODE-ED25519', namedCurve: 'NODE-ED25519' }, Miniflare fails with a DOMException with name == "NotSupportedError".

I've got a branch locally that fixes this that I'll PR in a bit :)