fix: polyfill Buffer for browser compatibility (#112)

* Polyfill with "buffer" and "assert" for browser environments
* Instead of relying on webpack to make this library browser compatible, we now use a buffer library that provides a polyfill when used in the browser

packages/ripple-binary-codec/test/utils.js

@@ -1,4 +1,5 @@
 const fs = require("fs");
+const { Buffer } = require('buffer/')
 
 function hexOnly(hex) {
   return hex.replace(/[^a-fA-F0-9]/g, "");