Examine source code of page_reloader

{
  "manifest_version": 2,
  "name": "page_reloader",
  "version": "1.1",
  "description": "Reloads local files every 5 seconds",
  "homepage_url": "https://github.com/k33theod/reloader",
  "icons": {
    "48": "icons/reload_48.png"
  },
  "applications": {
    "gecko": {
      "id": "k33theod@gmail.com"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "file://*/*",
        "http://localhost/*"
      ],
      "js": [
        "reload.js"
      ]
    }
  ]
}