Initial release candidate

[astromechza]

Required for initial release and platform con demo. In no particular order but making sure I don't forget about:

• [x] implement overrides path and file in the same way as score-compose
• [x] implement image override
• [x] generate single manifests file
• [x] implement a patch-manifests option as a basic way of overriding output manifest components
• [x] document the CLI help text
• [x] automated CLI unit testing
• [x] default resource provisioning for dns ~(using K8s external-dns)~, route (using gateway-api), and postgres
• [x] licence text
• [x] CI tooling
• [x] healthchecks on redis and pg
• [ ] more docs and examples