Examine source code of Parent Tab Switcher

{
  "browser_action": {
    "default_icon": "images/switch.png"
  },
  "homepage_url": "https://github.com/irvinm/Parent-Tab-Switcher",
  "manifest_version": 2,
  "name": "Parent Tab Switcher",
  "version": "0.9.0",
  "description": "An addon that allows you to switch between parent tabs.",
  "icons": {
    "128": "images/switch.png"
  },
  "applications": {
    "gecko": {
      "id": "Parent-Tab-Switcher@irvinm.addons.mozilla.org"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "tabs"
  ],
  "commands": {
    "next-tab-without-parent": {
      "suggested_key": {
        "default": "Ctrl+Alt+D"
      },
      "description": "Switch to the next parent tab."
    },
    "previous-tab-without-parent": {
      "suggested_key": {
        "default": "Ctrl+Alt+U"
      },
      "description": "Switch to the previous parent tab."
    }
  }
}