Feature request: disable CommonJS / ES5 / lib build

[treshugart]

Currently we only have a use case for using the UMD build. We want to disable building lib for a few reasons:

• It speeds up our builds by a wide margin (70+ components in a Lerna mono-repo)
• We currently use loaders, which makes exposing es / lib a problem for consumers because they must know about the implementation details.
• We point main to the umd bundles to get around ^, therefore we don't want to incur the overhead of es / lib at the moment.
• We do want to get rid of umd in the future and only use es / lib but that requires a lot of work to get rid of the loaders.

What I am proposing, in the form of a PR, is:

• Allow an npm.cjs option to be specified as false to switch off the CommonJS build

This means that even though it's a new feature, it's not a breaking change as the lib build will still be generated by default (opt-out).

[treshugart]

Implemented in fork while awaiting PR: https://www.npmjs.com/package/@treshugart/nwb.

[treshugart]

Closing because PR was merged. Thank you!

[insin]

Thanks for the PRs, aiming to cut a release of whatever's in master on Thursday morning (AEST)