Examine source code of GitHub Extension

{
  "name": "GitHub Extension",
  "description": "GitHub Browser Extension",
  "version": "1.0.0",
  "manifest_version": 2,
  "content_scripts": [
    {
      "matches": [
        "https://*/*",
        "http://*/*"
      ],
      "js": [
        "inject.js"
      ]
    }
  ],
  "browser_action": {
    "default_title": "GitHub Extension",
    "default_popup": "index.html"
  },
  "icons": {
    "16": "icons/16.png",
    "32": "icons/32.png",
    "48": "icons/48.png",
    "128": "icons/128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{27a81d80-0c01-43e8-8300-bb757003e81e}"
    }
  }
}