Examine source code of Markr

{
  "name": "Markr",
  "description": "Lets you highlight and capture content on web like a marker",
  "version": "0.1.7",
  "manifest_version": 2,
  "icons": {
    "16": "icons/markr_icon_16.png",
    "48": "icons/markr_icon_48.png",
    "128": "icons/markr_icon_128.png"
  },
  "browser_action": {
    "default_title": "markr",
    "default_popup": "popup/popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "content.css"
      ]
    }
  ],
  "permissions": [
    "activeTab",
    "contextMenus",
    "*://localhost/*",
    "*://markr.app/*",
    "*://my.markr.app/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  }
}