Examine source code of TruthLens

{
  "manifest_version": 2,
  "name": "TruthLens",
  "version": "1.0.1",
  "description": "Adds truthlens button on the page. You have to click the button to request truthlens service to get a trueness indication. If you want to get the trueness indication without pushing any button by sending the link the article you are reading, please consider our Auto TruthLens button.",
  "icons": {
    "48": "icons/tl-icon-48.png"
  },
  "applications": {
    "gecko": {
      "id": "shankar.narayan@truthlenscorp.com"
    }
  },
  "web_accessible_resources": [
    "images/tl-icon-16.png"
  ],
  "permissions": [
    "*://*/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://*/*"
      ],
      "js": [
        "button-adder.js"
      ]
    }
  ]
}