docs: added repostatus and crates badges

Author: ivanitskiy

README.md

@@ -1,4 +1,6 @@
 [![Rust](https://github.com/nginxinc/ngx-rust/actions/workflows/ci.yaml/badge.svg)](https://github.com/nginxinc/ngx-rust/actions/workflows/ci.yaml)
+[![Project Status: Concept – Minimal or no implementation has been done yet, or the repository is only intended to be a limited example, demo, or proof-of-concept.](https://www.repostatus.org/badges/latest/concept.svg)](https://www.repostatus.org/#concept)[![crates.io](https://img.shields.io/crates/v/ngx.svg)](https://crates.io/crates/ngx)
+
 
 ## Project status
 This project is still a work in progress and not production ready.