Be more restrictive with formats for URIs

[jamietanna]

When using https://www.npmjs.com/package/@stoplight/prism-cli, we get the following generated API:

{
  "api-version": "api.gov.uk/v1alpha",
  "apis": [
    {
      "api-version": "api.gov.uk/v1alpha",
      "data": {
        "contact": "nulla",
        "description": "ipsum adip",
        "documentation-url": "https://r4\"^)e",
        "name": "id incididunt",
        "organisation": "m",
        "url": "https://&F|(NJ7"
      }
    }
  ]
}

Notice that the https://.* doesn't give us valid formats.