Node.js 'crypto' module subset for browser

Package contents:

- Buffer
- getCiphers()
- createECDH()
- createCipher() (deprecated, use createCipheriv() instead)
- createCipheriv()
- createDecipher() (deprecated, use createDecipheriv() instead)
- createDecipheriv()
- pbkdf2
- pbkdf2Sync

Usage example:

``
const {
Buffer,
createECDH,
createCipheriv,
createDecipheriv,
pbkdf2,
pbkdf2Sync,
} = window.browserCrypto;
// import {
// Buffer,
// createECDH,
// createCipheriv,
// createDecipheriv,
// pbkdf2,
// pbkdf2Sync,
// } from 'browser-crypto';

const ecdh1 = createECDH('secp256k1');
const ecdh2 = createECDH('secp256k1');

const publicKey1 = ecdh1.generateKeys();
const publicKey2 = ecdh2.generateKeys();

const secret1 = ecdh1.computeSecret(publicKey2);
const secret2 = ecdh2.computeSecret(publicKey1);

const iv = Buffer.alloc(16);
const data = Buffer.from('abcdef');

const cipher = createCipheriv('aes256', secret1, iv);
const encrypted = Buffer.concat([cipher.update(data), cipher.final()]);

const decipher = createDecipheriv('aes256', secret2, iv);
const decrypted = Buffer.concat([decipher.update(encrypted), decipher.final()]);
console.log(decrypted.toString());

pbkdf2('password', 'salt', 1, 32, 'sha512', (error, derivedKey) => {
if (error) throw error;
console.log(derivedKey);
});

const derivedKey = pbkdf2Sync('password', 'salt', 1, 32, 'sha512');
console.log(derivedKey);

``