remove setting contract on window object and tweak webpack config

Author: eggplantzzz

packages/contract/webpack.config.js

@@ -27,11 +27,9 @@ module.exports = {
     new webpack.ProvidePlugin({
       process: "process/browser"
     }),
-    })
   ],
   resolve: {
     fallback: {
-      buffer: require.resolve("buffer"),
       crypto: require.resolve("crypto-browserify"),
       http: require.resolve("stream-http"),
       https: require.resolve("https-browserify"),