Examine source code of Scroll Wheel Tab Switcher

{
  "manifest_version": 2,
  "name": "Scroll Wheel Tab Switcher",
  "version": "3.1.0",
  "description": "Switch tabs with Alt + mouse wheel anywhere on the page. Fast, focused, private tab scrolling for mouse or trackpad.",
  "browser_specific_settings": {
    "gecko": {
      "id": "@tabwheel.reklai",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "permissions": [
    "tabs",
    "storage",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "contentScript.js"
      ],
      "all_frames": true,
      "match_about_blank": true,
      "run_at": "document_start"
    }
  ],
  "options_ui": {
    "page": "optionsPage/optionsPage.html",
    "open_in_tab": true
  },
  "browser_action": {
    "default_icon": {
      "16": "icons/icon-16.png",
      "32": "icons/icon-32.png",
      "48": "icons/icon-48.png",
      "96": "icons/icon-96.png"
    },
    "default_popup": "toolbarPopup/toolbarPopup.html",
    "default_title": "Scroll Wheel Tab Switcher"
  },
  "icons": {
    "16": "icons/icon-16.png",
    "32": "icons/icon-32.png",
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png",
    "128": "icons/icon-128.png"
  }
}