mark the package as side effect free

[kubikowski]

Description:

Webpack, as well as some other bundlers, use the "sideEffects" package field in order to tell whether a package can optimally utilize tree shaking in the bundling process.

This library contains individual utilities. And each of those should be tree shakable by bundlers. If you only want to serve difference out of this package, you should be able to do so.

Resources:

• the webpack guide to tree shaking
• what does webpack expect from a package with "sideEffects" false
• a good conversation about whether or not to specify the "sideEffects" field