Add smol-rs logo (#52)

Author: notgull

src/lib.rs

@@ -8,6 +8,12 @@
 //! * [`Semaphore`] - limits the number of concurrent operations.
 
 #![warn(missing_docs, missing_debug_implementations, rust_2018_idioms)]
+#![doc(
+    html_favicon_url = "https://raw.githubusercontent.com/smol-rs/smol/master/assets/images/logo_fullsize_transparent.png"
+)]
+#![doc(
+    html_logo_url = "https://raw.githubusercontent.com/smol-rs/smol/master/assets/images/logo_fullsize_transparent.png"
+)]
 
 /// Simple macro to extract the value of `Poll` or return `Pending`.
 ///