Examine source code of Miralearn

{
  "browser_action": {
    "default_icon": {
      "16": "/images/Miralearn_extension_icon_16.png",
      "32": "/images/Miralearn_extension_icon_32.png",
      "48": "/images/Miralearn_extension_icon_48.png",
      "64": "/images/Miralearn_extension_icon_64.png",
      "96": "/images/Miralearn_extension_icon_96.png",
      "128": "/images/Miralearn_extension_icon_128.png",
      "256": "/images/Miralearn_extension_icon_256.png"
    }
  },
  "default_locale": "en",
  "icons": {
    "16": "/images/Miralearn_extension_icon_16.png",
    "32": "/images/Miralearn_extension_icon_32.png",
    "48": "/images/Miralearn_extension_icon_48.png",
    "64": "/images/Miralearn_extension_icon_64.png",
    "96": "/images/Miralearn_extension_icon_96.png",
    "128": "/images/Miralearn_extension_icon_128.png",
    "256": "/images/Miralearn_extension_icon_256.png"
  },
  "background": {
    "scripts": [
      "backgroundRun.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "all_frames": true
    }
  ],
  "description": "__MSG_appDesc__",
  "manifest_version": 2,
  "name": "__MSG_appName__",
  "permissions": [
    "tabs",
    "webNavigation"
  ],
  "version": "0.1.2",
  "web_accessible_resources": [
    "<all_urls>",
    "css/*",
    "images/*",
    "fonts/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{565bd6df-d71f-4ff9-9272-b72e77e0efb6}"
    }
  }
}