Add README instructions for installing ibverbs related packages for tensor engine (#596)

Summary:
Pull Request resolved: #596

Adds a few missing instructions for how to build monarch with tensor engine

Reviewed By: zdevito

Differential Revision: D78665299

fbshipit-source-id: ac5673f527afca9558d2f7cf4f393030870ec5f6

Author: allenwang28

README.md

@@ -42,6 +42,9 @@ sudo dnf install clang-devel libnccl-devel
 conda install -c conda-forge clangdev nccl
 conda update -n monarchenv --all -c conda-forge -y
 
+# If you are building with RDMA support, build monarch with `USE_TENSOR_ENGINE=1 pip install --no-build-isolation .` and dnf install the following packages
+sudo dnf install -y libibverbs rdma-core libmlx5 libibverbs-devel rdma-core-devel
+
 # Install build dependencies
 pip install -r build-requirements.txt
 # Install test dependencies