Add more folders to .npmignore

[NicolasCARPi]

Hello,

Installing 3Dmol.js with npm results in a 40 Mb folder. Looking into the size distribution, we can see that a lot of space is used by the python stuff:

And we definitely don't need all these examples and non-production code when installing the package. Especially the notebooks chekpoints!

So here is a PR that will make the npm install lighter.

Here is how it looks before:

And after:

As a side note, I would suggest splitting the python code into another repository, as I believe it makes more sense to separate JS and Python projects, which have different tooling and environments.

[codecov[bot]]

Codecov Report

Merging #665 (d192d46) into master (93a2944) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #665   +/-   ##
=======================================
  Coverage   83.04%   83.04%           
=======================================
  Files         141      141           
  Lines       11445    11445           
  Branches     2106     2106           
=======================================
  Hits         9504     9504           
  Misses       1609     1609           
  Partials      332      332           

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[NicolasCARPi]

Thanks for the rapid merge @dkoes. Now we can test the new github action to publish a new package? :)