Add build process for pulling in templates from coder/registry

[f0ssel]

• Validate and parse templates ( maybe copy over from coder/coder)
• What does releases for starter templates look like? In RFC we decided no versioning for now
• No community templates for coder namespace in coder/registry repo
• Add coder/registry templates data to frontend data payload

[bcpeinhardt]

#545 is the ticket for moving templates into coder/registry. It would be nice to outline the exact structure here in order to do these in parallel.
I think the structure will be registry/registry/<namespace>/templates/<template-directory> where the template directory matches the structure of the template directory in coder/coder/examples/templates.

[bcpeinhardt]

PR to close: https://github.com/coder/registry-server/pull/229
Dependent on #545