Source links are out of date and broken

[cjsmith]

The source links for the function source code are out of date and broken.

Eg the source link for https://github.com/javascriptdata/danfojs-doc/blob/master/api-reference/series/series.dropna.md links to https://github.com/opensource9ja/danfojs/blob/master/danfojs/src/core/series.js#L93 which results in a 404 if you click it.

I have fixed these on a commit in a fork off of masterand would be happy to submit a PR if you're interested.

I just wasn't sure if these docs are autogenerated somehow. If you would accept a PR, should I use a hash or tag so that the docs point to a specific commit and don't get out of date or should I use master and then at least the source will point to the latest version?

Thanks,

Colin