Examine source code of Meta tags inspector

{
  "description": "Adds a new panel to the developer tools. This panel can inspect metatags.",
  "manifest_version": 2,
  "name": "Meta tags",
  "version": "1.0",
  "author": "Roy Ermers",
  "homepage_url": "https://github.com/mdn/webextensions-examples/tree/master/devtools-panels",
  "icons": {
    "48": "icons/tag.svg"
  },
  "background": {
    "scripts": [
      "background_scripts/background.js"
    ]
  },
  "permissions": [
    "<all_urls>"
  ],
  "devtools_page": "devtools/devtools-page.html"
}