Examine source code of Comment Locator

{
  "manifest_version": 2,
  "name": "Comment Locator",
  "version": "1.2resigned1",
  "author": "Rob Hoelz",
  "homepage_url": "https://github.com/hoelzro/fx-comment-locator",
  "description": "Adds a marker next to the scrollbar indicating how far down on the page the comments are",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "comment-locator.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{f7773401-e525-43f4-84c8-24bfe665b06d}"
    }
  }
}