Update agent.mdx

Starting from Consul v1.20.1+ent, Consul supports using Azure Blob Storage for the snapshot agent via Azure Service Principal  ID and Secret authentication. I've successfully tested this configuration in my lab environment and have added the relevant parameters to this documentation for completeness.

website/content/commands/snapshot/agent.mdx

@@ -396,9 +396,15 @@ These options cannot be used when using `backup_destinations` in a config file.
 - `-azure-blob-container-name` - Container to use. Required for Azure blob storage, and setting this
   disables local storage.
 
-* `-azure-blob-environment` - Environment to use. Defaults to AZUREPUBLICCLOUD. Other valid environments
+- `-azure-blob-environment` - Environment to use. Defaults to AZUREPUBLICCLOUD. Other valid environments
   are AZURECHINACLOUD, AZUREGERMANCLOUD and AZUREUSGOVERNMENTCLOUD. Introduced in Consul 1.7.3.
 
+~> These below options `azure-blob-service-principal-id`, `azure-blob-service-principal-secret`, and `azure-blob-tenant-id` are introduced in v1.20.1+ent.
+
+- `-azure-blob-service-principal-id` and `-azure-blob-service-principal-secret` - Use these parameters to authenticate using Service Principal (SPN) ID + Secret together.
+
+- `-azure-blob-tenant-id` - Required when using Service Principal ID and Secret.
+
 #### Google Cloud Storage options
 
 ~> This option is deprecated when used with a top-level `google_storage` object in a config file. Use `snapshot_agent -> backup_destinations -> google_storage[0]` in a config file instead.