Reduce published npm package size

[Munawwar]

Hi. First off, this is a very useful library. Thanks for the work.

I see some huge files has made it into the final npm package published - https://www.npmjs.com/package/csvtojson?activeTab=code
You can see that the coverage/ directory is 6 MB in size. Also .nyc_output etc. However the code base has an .npmignore file with coverage/ directory to be excluded. So what happened there?

Regards