feat: add serviceinfo endpoint

[AlpinDale]

As discussed offline with @db0 and @LostRuins, we want to establish a well-known URI for LLM inference APIs. The URI will be named serviceinfo, and will be accessible at the /.well-known/serviceinfo route on the RESTful API server.

The overall structure looks like this:

{
  "version": 1.0,
  "software": {
    "name": "string",
    "version": "string",
    "repository": "url",
    "homepage": "url",
    "logo": "url"
  },
  "api": {
    "api_name_1": {
      "name": "string",
      "base_url": "url",
      "documentation": "url",
      "version": 0
    },
    "api_name_2": {
      "name": "string", 
      "base_url": "url",
      "documentation": "url",
      "version": 0
    }
  }
}

The current standard for this serviceinfo if 1.0. Software information will go in the software part, and individual support API schemes will go into the api part. An example for Aphrodite Engine looks like this:

{
  "version": 0.1,
  "software": {
    "name": "Aphrodite Engine",
    "version": "0.6.3.post1",
    "repository": "https://github.com/PygmalionAI/aphrodite-engine",
    "homepage": "https://aphrodite.pygmalion.chat",
    "logo": "https://pygmalion.chat/icons/favicon.ico"
  },
  "api": {
    "openai": {
      "name": "OpenAI API",
      "base_url": "http://localhost:2242/v1",
      "documentation": "http://localhost:2243/redoc",
      "version": 1
    },
    "koboldai": {
      "name": "KoboldAI API",
      "base_url": "http://localhost:2242/api",
      "documentation": "http://localhost:2243/redoc",
      "version": 1
    }
  }
}