Dropped .npmignore

[mcollina]

Fixes #24

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[L2jLiga]

lgtm

[delvedor]

LGTM

[kibertoad]

@mcollina Shouldn't files be added to package.json then? Now we are going to be publishing plenty of additional noise files, which can be undesired, especially for browser usage.

[mcollina]

they won't be included in the bundle anyway - we are talking about 4KB that will be downloaded and placed on disk during development.

Managing .npmignore and/or files is just awkward, I just prefer to have all contents pushed.