webpack@4 / webpack@next will support package.json:sideEffects: false wherein libraries can indicate their ESM re-exports are side effect free and can be much more efficiently removed for smaller, faster final bundles. (#465)

Lodash has already rolled out this change in
https://unpkg.com/[email protected]/package.json

## Issues

This was originally uncovered / discussed at length in:

* webpack/webpack#1750

This PR should resolve the issues discussed in:

* FormidableLabs/victory#549
* FormidableLabs/redux-little-router#262

## Changes

* Add `sideEffects: false` to `package.json` to allow webpack4 tree-shaking to actually remove all unused code.

> This PR has been automatically opened by your friendly [`multibot`](https://github.com/FormidableLabs/multibot/). The transform code and documentation is available at: https://github.com/FormidableLabs/multibot-examples/tree/master/transforms/webpack-side-effects

Author: ryan-roemer

package.json

@@ -109,5 +109,6 @@
       "raf/polyfill",
       "<rootDir>/jest-setup.js"
     ]
-  }
+  },
+  "sideEffects": false
 }