Add MELPA badges.

Author: grafov

README.md

@@ -1,5 +1,7 @@
 <!--*- mode:markdown;mode:orgtbl;fill-column:99 -*-->
-# rust-playground [WIP]
+# rust-playground [![MELPA Stable](https://stable.melpa.org/packages/rust-playground-badge.svg)](https://stable.melpa.org/#/rust-playground) [![MELPA](https://melpa.org/packages/rust-playground-badge.svg)](https://melpa.org/#/rust-playground)
+
+*It works. But development still in progress!*
 
 GNU/Emacs mode that setup local playground for code snippets in Rust
 language.  This is a port of