Draft: Add a schema for owners.yaml

It is important that the data in info/owners.yaml is consistent. The golang programs included in this repo do some basic validation of the file but it is somewhat cumbersome.

Here a simple schema is provided that defines the expected structure and properties of the owners.yaml document. It uses the standard specification from https://json-schema.org.

The current owners.yaml has several errors and does not conform to this schema until !690 (merged) is merged.

Part of: #114

Signed-off-by: Patrick Talbert ptalbert@redhat.com