Added PingCaps Rust RocksDB and ObjectiveRocks (#4065)

Summary:
1. I added PingCap's more up-to-date Rust Binding of RocksDB
2. I also added ObjectiveRocks which is a very nice binding for _both_ Swift and Objective-C
Closes https://github.com/facebook/rocksdb/pull/4065

Differential Revision: D8670340

Pulled By: siying

fbshipit-source-id: 3db28bf3a464c3e050df52cc92b19248b7f43944

LANGUAGE-BINDINGS.md

@@ -10,9 +10,11 @@ This is the list of all known third-party language bindings for RocksDB. If some
 * PHP - https://github.com/Photonios/rocksdb-php
 * C# - https://github.com/warrenfalk/rocksdb-sharp
 * Rust
+    * https://github.com/pingcap/rust-rocksdb (used in production fork of https://github.com/spacejam/rust-rocksdb)
     * https://github.com/spacejam/rust-rocksdb
     * https://github.com/bh1xuw/rust-rocks
 * D programming language - https://github.com/b1naryth1ef/rocksdb
 * Erlang - https://gitlab.com/barrel-db/erlang-rocksdb
 * Elixir - https://github.com/urbint/rox
 * Nim - https://github.com/status-im/nim-rocksdb
+* Swift and Objective-C (iOS/OSX) - https://github.com/iabudiab/ObjectiveRocks