changed async example to use spawn_blocking

The correct way to call blocking code in tokio is through the spawn_blocking mechanism to prevent all threads from being exhausted to perform async operations. See below for details.
look [here](https://users.rust-lang.org/t/nano-get-minimalistic-http-s-get-crate/37264/2?u=rapidclock)

README.md

@@ -2,7 +2,7 @@
 [![Crates.io](https://img.shields.io/crates/v/nano-get.svg)](https://crates.io/crates/nano-get)
 [![Docs.rs](https://docs.rs/nano-get/badge.svg)](https://docs.rs/nano-get)
 
-A tiny implementation of HTTP GET using only the standard library by default.
+A minimalistic implementation of HTTP GET using only the standard library by default.
 
 If you require `https`, please enable the `"https"` feature flag like:
 ```
@@ -121,7 +121,7 @@ This is also not meant to be demonstrative of idiomatic uses of the async librar
 ```toml
 [dependencies]
 nano-get = {version = "0.2.3", features = ["https"] }
-tokio = { version = "0.2.6", features = ["rt-threaded"] }
+tokio = { version = "0.2.10", features = ["blocking", "rt-threaded"] }
 futures = "0.3.1"
 ```
 
@@ -135,7 +135,6 @@ use std::time::Instant;
 
 use tokio::runtime::{Runtime, Builder};
 use futures::future::try_join_all;
-use nano_get::get;
 
 fn main() {
     let mut runtime: Runtime = Builder::new().threaded_scheduler().build().unwrap();
@@ -145,7 +144,7 @@ fn main() {
         let start = Instant::now();
         for i in 1..=100 {
             let url = format!("{}/{}", base_url, i);
-            handles.push(tokio::spawn(get_url(url)));
+            handles.push(tokio::task::spawn_blocking(move || nano_get::get(url)));
         }
         let responses: Vec<String> = try_join_all(handles).await.unwrap();
         let duration = start.elapsed();
@@ -154,10 +153,6 @@ fn main() {
         println!("Average time for get is: {}s", duration.as_secs_f64() / (responses.len() as f64));
     });
 }
-
-async fn get_url(url: String) -> String {
-    get(url)
-}
 ```
 
 **example output**
@@ -168,6 +163,6 @@ async fn get_url(url: String) -> String {
   "id": 100,
   "title": "enim repellat iste"
 }
-Time elapsed in http get is: 3.671184788s
-Average time for get is: 0.03671184788s
+Time elapsed in http get is: 1.171043748s
+Average time for get is: 0.01171043748s
 ```