`sideEffects: false` to package.json

Hello! :)

Would it make sense to add `sideEffects: false` to this library's `package.json`? This can enable more tree-shaking, in some cases: [documentation](https://github.com/webpack/webpack/blob/main/examples/side-effects/README.md) ([more detailed documentation](https://github.com/webpack/webpack.js.org/blob/6bc07960d30b7c534d809de86f1d611e9973af37/src/content/guides/tree-shaking.mdx))