[project] include dist folder during NPM publishing

[Alchez]

This should potentially fix the issues we're seeing with CI builds, as noted here, as well as setting up working environments as noted here.

Context:
We ignored the dist folders in the .gitignore file in #116, but NPM actually uses that as a fallback measure to decide what should show up in the packaged files in NPM. Since our entrypoints rely on the dist folder existing, new installs of our packages fail.

Solution:
I added an .npmignore file to apply most of the rules/patterns in our .gitignore file, but allow publishing the dist folder as well. This way, our development can still avoid build files and our packages can ship with the distributables.

Test:
If you install @stonecrop/atable in a new project and try to import anything from it, it'll fail trying to resolve the object. I tested the .npmignore on my fork of Stonecrop and I was able to install and import objects without an issue.