Add prefect.yaml support deployment schema

[EmilRex]

Describe the current behavior

When authoring a prefect.yaml file for the purposes of creating deployments, users must refer to documentation and source code in order to understand the schema of the file.

Describe the proposed behavior

Similar to how we maintain a schema file for settings, it would be useful to maintain a schema file for prefect.yaml. This would allow us to have syntax support in various IDEs through SchemaStore.

Example Use

No response

Additional context

See also:

• Schema reference in docs
• Update prefect.yaml formatter schema #12261

[olearycrew]

Idea that is maybe better as its own issue but related - what would the thoughts be on adding a command like:

prefect deployment init

that creates a skeleton prefect.yaml for folks?