Module for Azure Event Grid

Publish a module to Terraform Registry that helps to deploy Azure CosmosDb account.

Related Terraform resources:
- https://www.terraform.io/docs/providers/azurerm/r/eventgrid_domain.html
- https://www.terraform.io/docs/providers/azurerm/r/eventgrid_event_subscription.html
- https://www.terraform.io/docs/providers/azurerm/r/eventgrid_topic.html

Start by reviewing the issue's linked azurerm documentation for eventgrid_domain, eventgrid_event_subscription, and eventgrid_topic. Clarify the mismatch between the Azure Event Grid title and the CosmosDb account description, then define the module's scope and registry publication requirements. Done means a working module is published to the Terraform Registry.

Written by the indexing model from the issue text.