Examine source code of Easy Character Counter

{
  "version": "0.0.2",
  "manifest_version": 2,
  "default_locale": "en",
  "background": {
    "scripts": [
      "js/background.js"
    ]
  },
  "permissions": [
    "*://*/*",
    "contextMenus"
  ],
  "icons": {
    "64": "img/icon_64.png",
    "128": "img/icon_128.png",
    "512": "img/icon_512.png"
  },
  "content_scripts": [
    {
      "all_frames": false,
      "css": [
        "css/contents.css"
      ],
      "js": [
        "plugin/jquery.min.js",
        "js/contents.js"
      ],
      "matches": [
        "http://*/*",
        "https://*/*"
      ],
      "run_at": "document_idle"
    }
  ],
  "name": "__MSG_extensionName__",
  "description": "__MSG_extensionDescription__",
  "web_accessible_resources": [
    "img/close_w.svg"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{c6a8cf3e-e325-4b33-a9f7-316afcb4e8ac}"
    }
  }
}