docs: add note on installing cuda version of Reactant on login nodes (#276)

Author: avik-pal

README.md

@@ -63,3 +63,15 @@ Reactant.set_default_backend("gpu")
 # ones favorite code will now all be executed on GPU, no CUDA.jl dependency even required!
 ```
 
+## Installing Reactant on GPU Servers without Internet
+
+If you want to use Reactant on GPU Servers where all packages must be installed on the login nodes and the compute nodes don't have access to internet,
+add the following to the Project.toml and precompile the package:
+
+```toml
+[extras]
+Reactant_jll = "0192cb87-2b54-54ad-80e0-3be72ad8a3c0"
+
+[preferences.Reactant_jll]
+gpu = "cuda"
+```