Asn1 validator node ed25519

[aljones15]

Adds:

• ASN1 validators for der format ed25519 public and private keys
• Adds the OID for ed25519 keys
• Adds extract functions so node 12 ed25519 keys can be imported now.

[dlongley]

Some of the docs in here make it seem like the functions are specific to node.js buffers, etc. -- when they aren't. The docs can mention that if you're using node's API that the functions will be particularly helpful, but they should lead by saying that the functions, for example, convert a DER-formatted PKCS#8 private key to a raw private key.

We may also want the functions to be something like publicKeyFromDer() and publicKeyToDer() ... or something that more closely approximates existing the forge API. I think we need a short bikeshedding around. cc: @mattcollier, @davidlehn

[aljones15]

@mattcollier sorry you had to change those consts but thanks for updating this.

[mattcollier]

@dlongley @aljones15 I'll handle Longley's comments.

[mattcollier]

@davidlehn I leave it to you to approve/merge and publish this. I'm not an owner on NPM. Thanks!

[aljones15]

@dlongley @mattcollier this can be closed correct? another PR added this feature I believe.

[dlongley]

I don't know what the status is, but so we can better track it I'm linking to that other PR: #697.

[davidlehn]

#697 was merged and released causing conflicts here. If some of this patch should still be merged, please rebase and update as needed.

[aljones15]

if I recall correctly this PR is not needed because it turns out the ed25519 keys use a common DER format that we already have a validator for. I believe this can be closed @dlongley