README.md: Add crate badge

Author: nadzyah

README.md

@@ -1,5 +1,7 @@
 # net-tools-rs
 
+[![crate][crate-image]][crate-link]
+
 Rust implementation of [net-tools](https://sourceforge.net/projects/net-tools/).
 
 The status of implemented commands is tracked in
@@ -10,3 +12,8 @@ https://github.com/rust-swifties/net-tools-rs/issues/3
 Compliance tests verify that net-tools-rs commands behave identically to the original
 net-tools implementation. See [compliance-tests/README.md](compliance-tests/README.md) for
 details on running the tests.
+
+[//]: # (badges)
+
+[crate-image]: https://img.shields.io/crates/v/net-tools-rs?logo=rust
+[crate-link]: https://crates.io/crates/net-tools-rs