LANGUAGE-BINDINGS.md: add another rust binding

Summary:
I made another rust binding. 👻

* Use C++ API (instead of C API)
* Try to follow [Rust Guidelines](https://aturon.github.io/README.html)
* Working in progress (the APIs are not stable yet)
Closes https://github.com/facebook/rocksdb/pull/2438

Differential Revision: D5690612

Pulled By: siying

fbshipit-source-id: 11d3956c33b5e5366555afbf3786b782be3046e7

LANGUAGE-BINDINGS.md

@@ -9,5 +9,7 @@ This is the list of all known third-party language bindings for RocksDB. If some
 * Haskell - https://hackage.haskell.org/package/rocksdb-haskell
 * PHP - https://github.com/Photonios/rocksdb-php
 * C# - https://github.com/warrenfalk/rocksdb-sharp
-* Rust - https://github.com/spacejam/rust-rocksdb
+* Rust
+    * https://github.com/spacejam/rust-rocksdb
+    * https://github.com/bh1xuw/rust-rocks
 * D programming language - https://github.com/b1naryth1ef/rocksdb