Add descriptions in JSON schemas to display relevant information in VSCode hovers

[garrytrinder]

VS Code will use the standard description field from the JSON Schema specification in order to provide information about properties on hover and during autocomplete.

If you want your descriptions to support formatting like links, you can opt in by using Markdown in your formatting with the markdownDescription property.

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "properties": {
    "name": {
      "type": "string",
      "description": "The name of the entry",
      "markdownDescription": "The name of the entry. [See the documentation](https://example.com)"
    }
  }
}

Note that markdownDescription is not part of the JSON schema specification but a VS Code-specific schema extension.

Source: https://code.visualstudio.com/Docs/languages/json#_use-rich-formatting-in-hovers

We should look at where we can provide rich descriptions with links to our documentation.