Examine source code of TabSubmit Basic

{
  "manifest_version": 2,
  "name": "TabSubmit Basic",
  "applications": {
    "gecko": {
      "id": "jid1-KR7YJG7ASAuPHQ@jetpack",
      "strict_min_version": "48.0"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "description": "Makes forms open in new tabs if you're holding down a meta key while you click.",
  "version": "0.5.0"
}