JSON-LD / RDF support

该 issue 未指明仓库文件、测试或入口点。首先追踪 API 如何处理 Accept 标头和响应格式，然后确定 JSON-LD 表示形式以及本体范围。完成的要求是形成一致认可的实现计划，并支持所请求的 JSON-LD 形式。

I think it would be valuable to be able to use a PokéAPI endpoint as a canonical URL within RDF linked data, so other RDF documents can refer to Pokémon concepts. For example, someone could make character bios using JSON-LD that look like:

{
  "@context": {
    "@vocab": "https://schema.org/",
    "pkmn": "https://pokemonkg.org/ontology/version/1.0.0"
  },
  "@id": "<...>",
  "@type": "Person",
  "name": "Meowth",
  "description": "Team Rocket's Meowth",
  "url": "https://bulbapedia.bulbagarden.net/wiki/Meowth_(Team_Rocket)",
  "pkmn:species": { "@id": "https://pokeapi.co/api/v2/pokemon-species/meowth" },
  "gender": { "@id": "https://schema.org/Male" },
  "memberOf": {
    "@type": "Organization",
    "name": "Team Rocket",
    "url": "https://bulbapedia.bulbagarden.net/wiki/Team_Rocket"
  },
  "knows": {
    "@id": "<...>",
    "@type": "Person",
    "name": "Meowzie",
    "url": "https://bulbapedia.bulbagarden.net/wiki/Meowzie",
    "pkmn:species": { "@id": "https://pokeapi.co/api/v2/pokemon-species/meowth" },
    "gender": { "@id": "https://schema.org/Female" }
  }
}

This would be very useful for creating original characters in a somewhat-standard machine-readable format, e.g. for use in TTRPG campaigns.

Some notes:

• There is a readily available Pokémon ontology for RDF, but we could extend it or make our own for PokéAPI if it doesn't have all the features we need.
• In the example above, I used the Person type from Schema.org (https://schema.org/Person) as it integrates with the rest of the Schema.org ontology - for example, the CreativeWork.character property takes a Person as its value to represent a character within a creative work. However, the Comic Book Ontology also provides a dedicated Character type (https://comicmeta.org/cbo/#Character).

Similar to MusicBrainz, a client could request the JSON-LD for a Pokémon concept by modifying its HTTP request in the following form:

GET /api/v2/pokemon-species/meowth HTTP/2
Host: pokeapi.co
Accept: application/ld+json

or alternatively append ?format=json-ld to the resource URL.