Download functionality, splitting into packages and a bit of refactoring

[NSEcho]

Hello, I have found your friend and I think it is really interesting. I made some changes, like using the go modules, changing the logic a bit and separating things into packages.

If you want to see any changes, feel free to let me know.

Greetings

[NSEcho]

Also, I have implemented functionality to download js files to some local directory, I will push the commit in a couple of hours