Examine source code of Find the elevation!

{
  "manifest_version": 2,
  "name": "Find the elevation!",
  "version": "1.1.0",
  "description": "Adds a red border to all webpages matching mozilla.org.",
  "icons": {
    "16": "icons/ico_m.png",
    "48": "icons/1.png"
  },
  "background": {
    "scripts": [
      "borderify.js"
    ]
  },
  "permissions": [
    "*://*.opentopodata.org/*",
    "*://*.google.com/maps/*",
    "menus",
    "search"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://*.mozilla.org/*",
        "*://*.opentopodata.org/*",
        "*://*.google.com/maps/*"
      ],
      "js": [
        "borderify.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{425ad80d-4a19-4223-b788-ade45406fd2e}"
    }
  }
}