Add link to IntelliJ Rust

Author: matklad

README.md

@@ -21,4 +21,5 @@ The dev-tools team does not cover rustc or Cargo, which are large and establishe
 * [Rustdoc](https://github.com/rust-lang/rust/tree/master/src/librustdoc)
 * [Clippy](https://github.com/Manishearth/rust-clippy)
 * [`bindgen`](https://github.com/servo/rust-bindgen/)
+* [IntelliJ Rust](https://github.com/intellij-rust/intellij-rust)
 * ... (TODO)