Document how to use osc.js with webpack

[colinbdclark]

As described in a comment on #86, it looks like osc.js can be used with webpack. However, we don't currently provide a simple set of instructions in the README explaining how to do so.

I'm not a webpack user, personally, but I'm hoping someone in the community can contribute some documentation based on their experience using it.

[cannoneyed]

Just figured out how to get this working using webpack to build for electron, which isn't a normal use case but I'm at least following up on the solution here for posterity. The key is to make webpack treat node_modules as external, so that the node process can use the native libs like serialport

I used webpack-node-externals:

const nodeExternals = require('webpack-node-externals');
...
module.exports = {
    ...
    externals: [nodeExternals()], // in order to ignore all modules in node_modules folder
    ...
};