Add a --harden option to the lint command to close down schemas

[jviotti]

Like enforcing additionalProperties: false, etc

[cbum-dev]

Hi @jviotti can I work on this issue?

[jviotti]

You can, but keep in mind that before even working on the CLI, we need the specific linting rules that would be enabled, which should be implemented here: https://github.com/sourcemeta/core/tree/main/src/extension/alterschema. And to do that, we first need to determine what the hardened rules even are...

I guess just forcing additionalProperties: false if additionalProperties is not used (unless unevaluatedProperties in 2019-09 and 2020-12) is a good one. I would expect a new harden folder in https://github.com/sourcemeta/core/tree/main/src/extension/alterschema.