Examine source code of Tab_Light

{
  "manifest_version": 2,
  "name": "TabLight",
  "version": "1.2",
  "description": "Hovering over a link will highlight already open tab instances.",
  "icons": {
    "48": "icons/tl-48.png"
  },
  "permissions": [
    "tabs",
    "activeTab",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "tablight.js"
      ]
    }
  ],
  "options_ui": {
    "page": "options.html",
    "open_in_tab": false
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{25bb92f0-67da-49dd-b9a0-0497059373f8}"
    }
  }
}