Guide for new contributors

[BugmanSpirit]

Could you make a how-to doc for adding new websites. For sites using already supported engines or sites that require a scrapper.

I don't have any android development experience but I know well enough java to write scrappers in jsoup or any other framework. The codebase makes somewhat sense to me. If there was a step by step guide on which classes to modify, where to place them, how are they being called, how to build and test, it would be really helpful.