Examine source code of BarterGGLink

{
  "manifest_version": 2,
  "name": "BarterGGLink",
  "version": "1.0",
  "description": "Adds a link to gg.deals on barter.vg game pages",
  "icons": {
    "48": "gg.png"
  },
  "permissions": [],
  "content_scripts": [
    {
      "matches": [
        "*://*.barter.vg/i/*"
      ],
      "js": [
        "ggDeals.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{3724f97b-6296-41d2-a97a-c68292391add}"
    }
  }
}