Add Schema for config file

[amai2012]

Describe the feature request

A JSON schema could be used to validate the config.yml for gatus.

Why do you personally want this feature to be implemented?

Aid in writing my own configuration files (see https://github.com/TwiN/gatus/issues/57)

Currently my pipeline deploying gatus has a just a yamllint step, which could be replaced by validating against the schema.

How long have you been using this project?

10 days

Additional information

No response

[amai2012]

Also it would be convenient to upload it to https://www.schemastore.org/json/ so users can comfortably use it in their IDE.