Examine source code of Shortcut Manager

{
  "manifest_version": 2,
  "name": "Shortcut Manager",
  "version": "1.0.0",
  "description": "Configure custom keys for firefox shortcuts to perform various browser actions.",
  "browser_specific_settings": {
    "gecko": {
      "id": "shortcut-manager@bonurtek.com",
      "strict_min_version": "64.0"
    }
  },
  "homepage_url": "https://github.com/bilalonur/shortcut-manager-extension",
  "author": "Bilal Onur Eskili",
  "icons": {
    "48": "img/icon48.png",
    "128": "img/icon128.png"
  },
  "permissions": [
    "storage",
    "tabs",
    "sessions"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "options_ui": {
    "page": "options.html",
    "browser_style": true,
    "open_in_tab": true
  },
  "commands": {
    "duplicate-tab": {
      "suggested_key": {
        "default": "Alt+Shift+D"
      },
      "description": "Duplicate the current tab"
    },
    "open-new-tab": {
      "suggested_key": {
        "default": "Ctrl+T"
      },
      "description": "Open a new tab"
    },
    "open-recent-closed-tab": {
      "suggested_key": {
        "default": "Alt+Shift+T"
      },
      "description": "Open the most recently closed tab"
    },
    "mute-tab": {
      "suggested_key": {
        "default": "Alt+Shift+M"
      },
      "description": "Mute or unmute the current tab"
    }
  },
  "browser_action": {
    "default_title": "Shortcut Manager",
    "default_popup": "popup.html"
  }
}