chore: Ignore the assets folder from being published to npm

[anshumanv]

Fixes #144

[gr2m]

This will ignore the assets folder altogether, not only for publish to npm. You either have to put it to .npmignore or you define a specific list of files / folders that you want to be published as described at https://docs.npmjs.com/files/package.json#files, which is what I’d prefer. Here is an example: https://github.com/octokit/rest.js/blob/master/package.json#L110-L115

[anshumanv]

Ah, I misunderstood the issue, made the changes, please see if this is appropriate. 👍

Thanks for the example though. :)

[gr2m]

👍 looks good :)