Examine source code of Weasyl Crossposter

{
  "manifest_version": 2,
  "name": "Weasyl Crossposter",
  "version": "1.0",
  "description": "Lets you easily crosspost images to Weasyl.",
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "activeTab",
    "tabs",
    "https://www.furaffinity.net/view/*",
    "https://inkbunny.net/s*",
    "https://www.weasyl.com/submit/visual*",
    "https://www.sofurry.com/view*",
    "https://www.deviantart.com/*/art*",
    "https://e621.net/posts/*",
    "https://twitter.com/*/status/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://www.furaffinity.net/view/*",
        "https://inkbunny.net/s*",
        "https://www.weasyl.com/submit/visual*",
        "https://www.sofurry.com/view*",
        "https://www.deviantart.com/*/art*",
        "https://e621.net/posts/*",
        "https://twitter.com/*/status/*"
      ],
      "js": [
        "jquery.min.js",
        "crossposter.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "jquery.min.js",
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": "icon.png",
    "default_title": "Furry Crossposter"
  }
}