Card builder

[nathanchu]

I think this was mentioned in some issue I cannot find anymore. There should be a card "builder" to make choosing a card easier.

[nathanchu]

I was starting to work on this, but it would be easier to build if there was a json api specification for this that could be requested that would have all of the api information on it, such as:

{
  "/api": {
    "params": [
      {
        "name": "username",
        "required": true,
        "default": null,
        "description": "Your username"
      }
    ]
  }
}

But obviously with all of the query params and routes. It could also be used to generate the readme if new PRs just added to the json file.

[rickstaa]

For future reference, @anuraghazra is working on implementing a URL builder with a live visual preview (see #1355 (comment)).