Support Ignoring Files

[baer]

https://github.com/substack/node-browserify#bignorefile
https://webpack.github.io/docs/webpack-for-browserify-users.html#ignore

[divmain]

This can be implemented as a simple plugin:

return opts => override => override("readSource", module =>
  module.path === opts.path ? "module.exports = {};" : override.CONTINUE
);

We can either provide this, along with a handful of other very simple plugins, or provide the solutions "cookbook" style.