Examine source code of git-expand

{
  "manifest_version": 2,
  "name": "git-expand",
  "description": "manifest.json description",
  "version": "0.1.0",
  "icons": {
    "16": "icon/16.png",
    "32": "icon/32.png",
    "48": "icon/48.png",
    "96": "icon/96.png",
    "128": "icon/128.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "git-expand",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "https://github.com/*"
      ],
      "css": [
        "content-scripts/pull.css"
      ],
      "js": [
        "content-scripts/pull.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{221462a1-7eb0-4048-bb78-50e24ecf730f}"
    }
  }
}