Function batch 

pub fn batch(urls: impl IntoIterator<Item = impl Into<String>>) -> BatchBuilder

Create a BatchBuilder for downloading multiple URLs concurrently.

Example

let results = kget::batch(["https://a.com/f1.zip", "https://b.com/f2.iso"])
    .concurrency(4)
    .output_dir("./downloads/")
    .download_all();