Basic support for export PKCS8

[giovanni9793]

Description

As a developer, I would like export the private key in PKCS #8. This is needed because some libraries accept only this format. This pull request adds the PrivateKeyPKCS8 interface which describe the structure of PKCS #8.

interface PrivateKeyPKCS8 {
  version: BNjs;
  privateKey: PrivateKeyPKCS1;
  privateKeyAlgorithm: { ecPublicKey: number[]; curve: number[] };
}

Type of Change

• New feature
• Bug fix
• API reference/documentation update
• Other

Does this introduce a breaking change?

No

Are documentation updates required?

• Changed interface name from 'PrivateKey' to 'PrivateKeyPKCS1';
• Added default parameter 'destinationFormatType' in 'encodePrivate' function.

Testing information

Tests added.

Checklist

• Code is commented where needed
• Unit test coverage for new or modified code paths
• npm run test passes
• Changelog is updated
• Tag 1 of @person1 or @Person2 (??? @zone117x )

[CLAassistant]

All committers have signed the CLA.

[giovanni9793]

CLA signed

[giovanni9793]

@shea256 some updates?

[giovanni9793]

I noticed that I did the commits with a different email, so I added that email and signed the CLA.
Hoping you'll accept the request.

[giovanni9793]

@kantai some news?

[zone117x]

@giovanni9793 the whitespace and formatting changes introduced in this PR make it difficult to review. Please revert unnecessary formatting changes and the org may have the bandwidth to review.

[giovanni9793]

@zone117x now should be ok, right?

[zone117x]

LGTM. Thanks @giovanni9793!

[zone117x]

https://www.npmjs.com/package/key-encoder/v/2.1.0-beta.0