Examine source code of Greendigger

{
  "manifest_version": 2,
  "name": "Greendigger",
  "version": "0.0.7",
  "description": "Helps you to find digs that are green. Inlines EPC (energy performance certificate) images on listing pages for Zoopla and Rightmove.",
  "icons": {
    "48": "logo/logo.png",
    "96": "logo/logo@2x.png",
    "144": "logo/logo@3x.png",
    "192": "logo/logo@4x.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.zoopla.co.uk/*",
        "*://*.rightmove.co.uk/*"
      ],
      "js": [
        "epc_inliner.user.js"
      ],
      "run_at": "document_end"
    }
  ],
  "permissions": [],
  "applications": {
    "gecko": {
      "id": "epc@tridactyl.xyz",
      "strict_min_version": "50.0"
    }
  }
}