Ignore optional dependencies

Prevent issues with fsevents and other breaking, platform-specific optionalDependencies in package.json by including this plugin first in the plugins stack.

Only points module sources to the empty module if it is found in package.json > optionalDependencies.

webpack.config.js

const ignoreOptional = require('webpack-ignore-optional');
{
  ...
  plugins: [
    ignoreOptional(),
    ...
  ],
}