Examine source code of OS Maps Street View

{
  "manifest_version": 2,
  "name": "OS Maps Street View",
  "version": "1.4",
  "description": "Adds a button to the pin popup on the OS Maps website providing a link to Google Maps Street View",
  "icons": {
    "48": "icons/osmapsstreetview-48.png"
  },
  "permissions": [
    "contextMenus",
    "webRequest",
    "tabs",
    "*://*.osmaps.com/*",
    "*://*.ordnancesurvey.co.uk/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "*://osmaps.ordnancesurvey.co.uk/*"
      ],
      "js": [
        "osmapsstreetview_legacy.js"
      ],
      "run_at": "document_start"
    },
    {
      "matches": [
        "*://explore.osmaps.com/*"
      ],
      "js": [
        "osmapsstreetview.js"
      ],
      "run_at": "document_start"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "osmapsstreetview@g733ckap.co.uk"
    }
  }
}