Add file list to package.json

[madhusudhand]

fusion-cli npm modules includes all the files from source which makes it heavy.
Hence included only required files.

[CLAassistant]

All committers have signed the CLA.

[KevinGrandon]

Thank you very much for the contribution. I think this is very close to what we want to do. I think we do have a few deeply nested test folders currently that might need to be ignored, possibly with the ! operator.

Would you be up for trying to negate those here? Otherwise we would be happy to pick it up ourselves.

E.g., https://github.com/fusionjs/fusion-cli/tree/master/build/babel-plugins/babel-plugin-chunkid/test

[madhusudhand]

@KevinGrandon added a generic negate rule "!**/test/" to ignore all the test directories under any directory not just 'build'. In case if we add test files for others later this will take care.

[madhusudhand]

Removed the optional entries README.md and LICENSE as per the review comments.

[rtsao]

I think sw.js is also missing. This leaves me thinking maybe we might want to use .npmignore instead, which would be the contents of .gitignore plus:

docs/
test/e2e
.github/
.buildkite/
.*

I'm wary of accidentally having necessary files being published, so perhaps it's better to instead explicitly say which files should not be published.