docs: added install instruction in Readme.md

Author: phenixcoder

README.md

@@ -1,11 +1,25 @@
 # Devops Scripts
 Collection of scripts to ease out some tasks duriing devops pipelines.
 
+## Instalation
+
+```shell
+npm i devops-scripts
+```
+Or Install globally
+> Recomended way is to install this module globally in your dev or ci/cd environment.
+```shell
+npm i -g devops-scripts
+```
+
 ---
 ## `terraform-cloud` / `tfc`
 Terraform cloud scripts
+### Environment Variables
+ - `TFC_TOKEN` : Terraform cloud Access Token
+ - `TFC_WORKSPACE` : Terraform cloud worksapce id. e.g. `ws-xxxxxxxxxx`
 
-Usage:
+### Usage:
 
 ```shell
 terraform-cloud <action> <resource> [arguments]