Examine source code of Piece Cost

{
  "manifest_version": 2,
  "name": "Piece Cost",
  "version": "0.3",
  "description": "A simple web extension to add the cost per piece to sets on lego.com",
  "icons": {
    "48": "icons/icon_48.png"
  },
  "permissions": [
    "*://*.lego.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://*.lego.com/*"
      ],
      "js": [
        "main.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{a55b7815-ef6d-4a0d-9284-10d1ec95626c}"
    }
  }
}