Include examples of ADT error-handling in project template

[jisantuc]

Right now it's up to users to figure out from tapir docs how to specify error outputs. This is a really common thing to do, so at least one endpoint should have an example of how it works.

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[jisantuc]

No, bad bot! This is still useful

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[pomadchin]

@jisantuc can we remove the angry bot out of this repo?