Examine source code of Userback

{
  "manifest_version": 2,
  "name": "Userback",
  "description": "Userback is a visual feedback & bug reporting tool for websites",
  "version": "5.1.0",
  "author": "Userback",
  "browser_action": {
    "default_icon": {
      "16": "/src/icons/icon16.png",
      "48": "/src/icons/icon48.png",
      "96": "/src/icons/icon96.png",
      "128": "/src/icons/icon128.png",
      "256": "/src/icons/icon256.png"
    },
    "default_title": "Userback",
    "default_popup": "/src/ui/popup/popup.html"
  },
  "icons": {
    "16": "/src/icons/icon16.png",
    "48": "/src/icons/icon48.png",
    "128": "/src/icons/icon128.png"
  },
  "background": {
    "scripts": [
      "/src/init.js",
      "/src/lib/browser-polyfill.min.js",
      "/src/background.js"
    ],
    "persistent": true
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "/src/init.js",
        "/src/lib/browser-polyfill.min.js",
        "/src/lib/snap.svg-min.js"
      ]
    },
    {
      "matches": [
        "https://*.app.userback.io/capture/*",
        "https://*.app.userback.io/viewer/*"
      ],
      "js": [
        "/src/content.js"
      ]
    },
    {
      "matches": [
        "https://app.userback.io/login/?redirect=extension",
        "https://app.userback.io/sso/callback/*"
      ],
      "js": [
        "/src/ui/popup/popup_login.js"
      ]
    }
  ],
  "web_accessible_resources": [
    "/src/lib/vumeter-processor.js"
  ],
  "permissions": [
    "notifications",
    "storage",
    "unlimitedStorage",
    "activeTab",
    "tabs",
    "contextMenus",
    "<all_urls>"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{fcff777b-82a5-4c33-a533-b86f6aec175e}"
    }
  }
}