Add URL to bip44-constants (js package)

slip-0044.md

@@ -88,6 +88,10 @@ index | hexa       | coin
 
 Coin types will be added only if there is a wallet implementing BIP-0044 for desired coin.
 
+##Libraries
+
+* [BIP44-constants](https://www.npmjs.com/package/bip44-constants) ([source](http://github.com/bitcoinjs/bip44-constants)) JavaScript package with described coin types
+
 ##References
 
 - [BIP-0044: Multi-Account Hierarchy for Deterministic Wallets](https://github.com/bitcoin/bips/blob/master/bip-0044.mediawiki)