fix: package main should be cjs format. (fixes #869)

[KholdStare]

Closes #869

• Add module entry for esm in package.json

See https://rollupjs.org/guide/en/#publishing-es-modules:

To make sure your ES modules are immediately usable by tools that work
with CommonJS such as Node.js and webpack, you can use Rollup to
compile to UMD or CommonJS format, and then point to that compiled
version with the main property in your package.json file. If your
package.json file also has a module field, ES-module-aware tools like
Rollup and webpack 2+ will import the ES module version directly.

[gabrieljablonski]

I'm not the most familiar with rollup, so we'll just take a look to make sure this doesn't break anything, though this is probably fine as is.

Thanks for the contribution.

[danielbarion]

hey o/

my fault, I totally forgot about this, I've worked in the past with an internal react components library for the company I worked for. This will probably work as expected.

I and @gabrieljablonski will test some use cases to double-check, thank you so much!

[danielbarion]

Hi guys, version 5.3.3-beta.0 was published from this PR, let's test and give feedback please, if it's working as expected 😄

[itsikcircle]

Still have this issue since "type": "module", still exists in the package.json file

react-tooltip.cjs.min.js is treated as an ES module file as it is a .js file whose nearest parent package.json contains "type": "module" which declares all .js files in that package scope as ES modules.

[danielbarion]

@itsikcircle yeah, this is probably related like: #887