Designed an interface for the REST network requests

[muhib349]

Added one abstract class with mentioning methods. However, I'm not sure how you would like to design that's why methods will be changed as per requirements.

Addressing the issue #28

[AliAkberAakash]

Hey @muhib349 ,
Thanks for raising this. Yes, I need to come up with a good design for the interface. I'm a bit busy currently. You can come up with your design, we can then fit it to the needs of leafy.
Roughly, the methods should take in json (dart map) responses and json return responses. additionally they can have options, query params, files etc.

[muhib349]

Hi @AliAkberAakash,
I have added some implementation, will update based on your feedback. Thanks