Examine source code of Tab Manager pluss

{
  "name": "Tab Manager pro",
  "short_name": "Tab Manager pro",
  "version": "5.2.0",
  "manifest_version": 2,
  "offline_enabled": true,
  "description": "Quickly find open tabs, see all windows in one view, find duplicates and limit tabs per window. The best Tab Manager pro for Chrome.",
  "author": "stefanXO",
  "icons": {
    "16": "images/browsers16.png",
    "48": "images/browsers48.png",
    "64": "images/browsers64.png",
    "128": "images/browsers128.png",
    "256": "images/browsers256.png"
  },
  "permissions": [
    "tabs",
    "contextMenus",
    "storage"
  ],
  "optional_permissions": [
    "system.display"
  ],
  "incognito": "spanning",
  "background": {
    "scripts": [
      "vendor/babel-polyfill.js",
      "vendor/browser-polyfill.min.js",
      "outlib/background.js"
    ],
    "persistent": true
  },
  "browser_action": {
    "default_icon": {
      "16": "images/browsers16.png",
      "48": "images/browsers48.png",
      "64": "images/browsers64.png",
      "128": "images/browsers128.png",
      "256": "images/browsers256.png"
    }
  },
  "options_ui": {
    "page": "options.html"
  },
  "commands": {
    "_execute_browser_action": {
      "suggested_key": {
        "default": "Ctrl+Shift+M",
        "windows": "Ctrl+Shift+M",
        "mac": "Command+Shift+M"
      }
    },
    "switch_to_previous_active_tab": {
      "suggested_key": {
        "default": "Ctrl+Shift+Space",
        "windows": "Ctrl+Shift+Space",
        "mac": "Command+Shift+Space"
      },
      "description": "Switches to previously active tab"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{b5cff618-58af-4f08-971a-1212da4925ce}"
    }
  }
}