Add re-exported libs to README.md

Signed-off-by: Sina Mahmoodi <[email protected]>

Author: s1na

README.md

@@ -15,6 +15,14 @@ A collection of utility functions for ethereum. It can be used in node.js or can
 
 Most of the string manipulation methods are provided by [ethjs-util](https://github.com/ethjs/ethjs-util)
 
+---
+
+Additionally ethereumjs-util re-exports a few commonly-used libraries. These include:
+
+- `BN` ([bn.js](https://github.com/indutny/bn.js))
+- `rlp` ([rlp](https://github.com/ethereumjs/rlp))
+- `secp256k1` ([secp256k1](https://github.com/cryptocoinjs/secp256k1-node/))
+
 # LICENSE
 
 MPL-2.0