docs(gitlab): add comments to gitlab example

docs/10_advanced_examples/gitlab.md

@@ -6,7 +6,17 @@ Gitlab-CI Example for reading Secrets from Vault using vkv
 
 ```yaml
 variables:
-  VKV_VERSION: "0.4.0"
+  # vaults env vars
+  # all of vault env vars are supported (https://developer.hashicorp.com/vault/docs/commands#environment-variables)
+  # required:
+  VAULT_ADDR: ""
+
+  # optional
+  VAULT_NAMESPACE: ""
+  VAULT_TLS_SKIP_VERIFY: "true"
+
+  # vkv env vars
+  VKV_VERSION: "0.4.0" # https://github.com/FalcoSuessgott/vkv/releases/tag/v0.4.0
   VKV_EXPORT_PATH: "secrets"
   VKV_EXPORT_FORMAT: "export"
 
@@ -19,7 +29,7 @@ default:
     - curl -LO "https://github.com/FalcoSuessgott/vkv/releases/download/v${VKV_VERSION}/vkv_${VKV_VERSION}_linux_amd64.apk"
     # install vkv
     - apk add --allow-untrusted ./vkv_${VKV_VERSION}_linux_amd64.apk
-    # auth to vault (requires jwt auth configuration)
+    # auth to vault (requires jwt auth configuration, https://docs.gitlab.com/ee/ci/examples/authenticating-with-hashicorp-vault/)
     - export VAULT_TOKEN="$(vault write -field=token auth/jwt/login role="${CI_PROJECT_ROOT_NAMESPACE}" jwt="${VAULT_JWT_TOKEN}")"
     # source env vars into shell
     - eval $(vkv export)