add terraform-docs WSL install script to readme

Author: adamwhitingnhs

README.md

@@ -7,6 +7,15 @@ This repository is used to build the infrastructure the NDR. That is it's sole p
 - [Terraform](https://developer.hashicorp.com/terraform/install)
 - [Terraform docs](https://github.com/terraform-docs/terraform-docs)
 
+To install terraform-docs on WSL use the following command
+```
+curl -sSLo ./terraform-docs.tar.gz https://terraform-docs.io/dl/v0.20.0/terraform-docs-v0.20.0-$(uname)-amd64.tar.gz &&
+tar -xzf terraform-docs.tar.gz &&
+chmod +x terraform-docs &&
+sudo mv terraform-docs /usr/local/bin/terraform-docs &&
+rm terraform-docs.tar.gz
+```
+
 ## Installation
 
 ### pre-commit hook