doc: add doc-preview to the CONTRIBUTING.md (#1945)

CONTRIBUTING.md

@@ -359,6 +359,7 @@ Note: you can override the Open API description of a field with a custom descrip
 ## Documentation Best Practices
 
 - In our documentation, when a resource field allows a maximum of only one item, we do not format that field as an array. Instead, we create a subsection specifically for this field. Within this new subsection, we enumerate all the attributes of the field. Let's illustrate this with an example: [cloud_backup_schedule.html.markdown](https://github.com/mongodb/terraform-provider-mongodbatlas/blob/master/website/docs/r/cloud_backup_schedule.html.markdown?plain=1#L207)
+- You can check how the documentation is rendered on the Terraform Registry via [doc-preview](https://registry.terraform.io/tools/doc-preview).
 
 ### Creating Resource and Data source Documentation
 We autogenerate the documentation of our provider resources and data sources via [tfplugindocs](https://github.com/hashicorp/terraform-plugin-docs).