Examine source code of Simple Session Saver

{
  "manifest_version": 3,
  "name": "Session Saver",
  "description": "An extension that saves your current session's tabs",
  "version": "1.0",
  "icons": {
    "16": "img/16x16.png",
    "24": "img/24x24.png",
    "32": "img/32x32.png",
    "48": "img/48x48.png",
    "64": "img/64x64.png",
    "128": "img/128x128.png"
  },
  "background": {
    "scripts": [
      "app.js"
    ]
  },
  "commands": {
    "save": {
      "suggested_key": {
        "default": "Ctrl+Shift+Home",
        "mac": "Command+Shift+Z"
      },
      "description": "Saves all currently opened tabs"
    },
    "open": {
      "suggested_key": {
        "default": "Ctrl+Shift+Insert",
        "mac": "Command+Shift+X"
      },
      "description": "Opens all saved tabs"
    }
  },
  "permissions": [
    "storage",
    "tabs",
    "contextMenus",
    "notifications"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "mhochoy@session-saver-firefox"
    }
  }
}