Examine source code of Screenshttr

{
  "manifest_version": 2,
  "name": "Screenshttr",
  "author": "HamletDuFromage",
  "version": "0.0.1",
  "description": "Simple FOSS extension to screenshot all active tabs",
  "homepage_url": "https://github.com/HamletDuFromage/screenshttr",
  "icons": {
    "48": "icons/icon.svg",
    "96": "icons/icon.svg",
    "192": "icons/icon.svg"
  },
  "permissions": [
    "tabs",
    "downloads",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "js/browser-polyfill.min.js",
      "js/background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "js/browser-polyfill.min.js"
      ]
    }
  ],
  "browser_action": {
    "browser_style": true,
    "default_popup": "html/popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "screenshttr@hamletdufromage"
    }
  }
}