add Erlang to the list of language bindings

Summary:
small edit of the language binding file to add the Erlang binding.
Closes https://github.com/facebook/rocksdb/pull/2797

Differential Revision: D5722235

Pulled By: sagar0

fbshipit-source-id: 8ecd74996dad4cac19666783256cfa4d9ce09160

LANGUAGE-BINDINGS.md

@@ -13,3 +13,4 @@ This is the list of all known third-party language bindings for RocksDB. If some
     * 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