Added a bit more description to the way to contribute to this project.
Added a bit more description to the way to contribute to this project.

awkward/SDWebImage,zhang-yawei/SDWebImage,dreampiggy/SDWebImage,awkward/SDWebImage,dreampiggy/SDWebImage,dreampiggy/SDWebImage,awkward/SDWebImage,tualatrix/SDWebImage,rs/SDWebImage