manifest.json

{
  "name": "Hello World",
  "version": "1.0",
  "description": "The first extension that I made.",
  "browser_action": {
    "default_popup": "popup.html"
  },
  "permissions": [
    "http://www.flags.99k.org/*",
    "http://flags.99k.org/*"
  ]
}