fix(package.json): mark react-transition-group as side-effect free for webpack tree shaking

[setsun]

What

Add "sideEffects": false to package.json to hint to webpack based workflows that the package is side effect free. This allows react-transition-group to allow tree-shaking of its modules.

Reference: https://webpack.js.org/guides/tree-shaking/#mark-the-file-as-side-effect-free

[silvenon]

Wow, thank you!!!

[jquense]

🎉 This PR is included in version 2.6.1 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[billyjanitsch]

@setsun @silvenon Unfortunately this doesn't have any effect because react-transition-group only ships a CommonJS build. It would have to also ship an ESM build (and point to it with the module field in package.json) for {sideEffects: true} to do anything. Module-level tree-shaking isn't possible with CommonJS.

[setsun]

Ah interesting, that's good to know. This may warrant a follow up PR

[silvenon]

Actually, #455 already adds ESM (but it was missing sideEffects!), we just haven't merged it yet. I was really busy and honestly not really knowledgeable about modules, but now I'll take some time to properly review and merge it if it's all good. 🙂 I would appreciate another pair of eyes on that PR if anyone wants to help, GitHub allows non-collaborators to also review PRs. 😎