Add support for npm

[MaxGfeller]

npm is the package manager for JavaScript and it would be awesome if impress.js could be installed with it. This pull request adds the package.json file which is the basis for publishing it to npm.

If you're ok with it and this gets merged, you can easily publish this by just running npm publish.

[Pierstoval]

👍 I like it !

[FagnerMartinsBrack]

Hi @MaxGfeller , in an effort to clear up older issues/PRs we are pinging back to know if you are still tracking this request.

To give a little bit of context, recently a decision was made in the project to make the development more active and the first task is to clear up older PRs like this one to see if the OP is still interested in keep it going.

[FagnerMartinsBrack]

Closing due to the lack of feedback from the OP. If you want to work in the PR again, feel free to comment here to open up the discussion again.

In the meantime we will track this request on #426, publish on npm is something that only the maintainers can do.