feat: add scalingo.schema.json

[revolunet]

A json-schema proposal for the scalingo.json file. This allows linting and documentation from your editor.

Its been created manually from the docs and tested against various scalingo.json examples.

Once this file is published, we can add it to SchemaStore so every IDE can associate scalingo.json to the published schema.

Meanwhile, you can see it in action by adding "$schema":https://raw.githubusercontent.com/Scalingo/developers-documentation/ba2c542c3a8c77145445a942c1ffc14790ce8799/scalingo.schema.json to your scalingo.json. If you use VScode and the Red Hat YAML extension then you you should see documentation appear instantly.

Note: The addons.plan key provide some examples but no restriction on what you can set here. (would be cool to have an exhaustive list if possible)

Some examples:

[ksol]

👋🏼 Hello @revolunet, sorry for not getting back to you on this topic sooner, and thanks for the submission! I'll add this on our plate of things to review, but it's indeed something that we'd benefit from