Add template for data-plane HEAD operations

[catalinaperalta]

Clear and concise description of the problem

Some data-plane services define HEAD operations for their services. We currently have a template for ARM specs, but it would be great to also provide one for data-plane specs.

Examples of brownfield data-plane specs that include HEAD operations:

• App Config: head op
• File Storage: head op
• Web PubSub: head op
• Data Lake Storage: head op

Checklist

• [X] Follow our Code of Conduct
• [X] Check that this issue is about the Azure libraries for typespec. For feature request in the typespec language or core libraries file it in the TypeSpec repo
• [X] Read the docs.
• [X] Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

[markcowl]

est: 5