docs: crates.io badge

Author: xJonathanLEI

README.md

@@ -4,6 +4,8 @@
 
 **A Rust library for using scanners via the [eSCL protocol](https://mopria.org/spec-download) (scanning over network)**
 
+[![crates-badge](https://img.shields.io/crates/v/escl.svg)](https://crates.io/crates/escl)
+
 ## Features
 
 - [x] Scanner capabilities