Prepare for NPM publish

[Lustyn]

In the interest of making the project more accessible and adding easy installation, I proposed that we publish shittydl on NPM. This PR makes changes to do such.

Important notes:

• We recommend people start their server using cli.js instead of index.js following these commits. There is a warning when starting the server to denote such, but it is not required and the server will function as normal regardless.
• While not intended to be used as a such, it is now possible to use shittydl as a library in the form of an express app after you have supplied a config to the exported functions arguments.

[Lustyn]

Diffs look awful because of the way I exported index.