add nip06.

nip06.js

@@ -0,0 +1,16 @@
+import createHmac from 'create-hmac'
+import * as bip39 from 'bip39'
+
+export function privateKeyFromSeed(seed) {
+  let hmac = createHmac('sha512', Buffer.from('Nostr seed', 'utf8'))
+  hmac.update(seed)
+  return hmac.digest().slice(0, 32).toString('hex')
+}
+
+export function seedFromWords(mnemonic) {
+  return bip39.mnemonicToSeedSync(mnemonic)
+}
+
+export function generateSeedWords() {
+  return bip39.entropyToMnemonic(randomBytes(16).toString('hex'))
+}