feat: added uses of env-var secret in readme

Author: VishwajitNagulkar

docs/terraform_workflow.md

@@ -30,6 +30,7 @@ jobs:
         AWS_ACCESS_KEY_ID:  # Specify AWS Access key ID
         AWS_SECRET_ACCESS_KEY: # Specify AWS Secret Access key ID
         AWS_SESSION_TOKEN:  # Specify Session ID
+        env-vars: # Specify env variables. ex. '{"KEY1":"VALUE1", "KEY2":" ${{ secrets.VALUE2 }}"}'
 
 ```
 
@@ -55,6 +56,7 @@ jobs:
         destroy:            # If the value is set to true, the workflow proceeds to the destroy step. However, the default value is false
      secrets:
         AZURE_CREDENTIALS:  # Specify Azure credentilas
+        env-vars: # Specify env variables. ex. '{"KEY1":"VALUE1", "KEY2":" ${{ secrets.VALUE2 }}"}'
 ```
 
 #### Example of a Terraform workflow for a Digitalocean cloud provider
@@ -79,8 +81,7 @@ jobs:
         destroy:            # If the value is set to true, the workflow proceeds to the destroy step. However, the default value is false
      secrets:
       DIGITALOCEAN_ACCESS_TOKEN:       # Digitalocean token
-      SPACES_ACCESS_KEY_ID:     # Provide spaces access key id if required
-      SPACES_SECRET_ACCESS_KEY: # Provide spaces secret access key if required
+      env-vars: # Specify env variables. ex. '{"KEY1":"VALUE1", "KEY2":" ${{ secrets.VALUE2 }}"}'
 ```
 
 #### Example of a Terraform workflow for a GCP cloud provider
@@ -105,4 +106,5 @@ jobs:
         destroy:            # If the value is set to true, the workflow proceeds to the destroy step. However, the default value is false
      secrets:
       GCP_SA_KEY:           # GCP service account Secret access key
+      env-vars: # Specify env variables. ex. '{"KEY1":"VALUE1", "KEY2":" ${{ secrets.VALUE2 }}"}'
 ```