Using in-development features in snapcraft.yaml

[Lin-Buo-Ren]

I would like to see a reference to the currently existing passthrough keys and accepting values, which seems to be scattered throughout the forum:

• URL/contact fields in snap metadata - store - snapcraft.io
• License: “unknown” is not true - store - snapcraft.io
• New install/refresh API with the store - store - snapcraft.io