Examine source code of Heading tags

{
  "manifest_version": 2,
  "name": "My Addon",
  "version": "1.0",
  "description": "Description here.",
  "content_scripts": [
    {
      "matches": [
        "*://*.com/*"
      ],
      "js": [
        "javascript.js"
      ]
    }
  ]
}