Examine source code of Page Marker

{
  "manifest_version": 2,
  "name": "Page Marker",
  "version": "1.0.0",
  "description": "Highlight text and add sticky notes directly on any webpage. Your marks are saved automatically and sync across visits",
  "icons": {
    "16": "icon-16.png",
    "32": "icon-32.png",
    "48": "icon-48.png",
    "128": "icon-128.png"
  },
  "permissions": [
    "storage",
    "activeTab",
    "<all_urls>"
  ],
  "browser_action": {
    "default_icon": {
      "16": "icon-16.png",
      "32": "icon-32.png",
      "48": "icon-48.png",
      "128": "icon-128.png"
    },
    "default_title": "Page Marker",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "content.css"
      ],
      "run_at": "document_end"
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{54c686d8-be24-4a9c-892a-56a67950418b}"
    }
  }
}