Hacktoberfest: Add custom URL metadata to libraries

[apacheli]

Specification:

{
  "name": "library",
  "urls": {
    "homepage": "example.com/homepage",
    "documentation": "example.com/documentation",
    "discord": "example.com/redirect-to-your-discord-server-invite-link",
    "others": {
      "patreon": "etc, etc"
    }
  }
}

Hacktoberfest is currently live on this repository, so feel free to start contributing 🚀 (see guide here)