Examine source code of Auto Fullscreen

{
  "description": "Open all Firefox windows in full screen mode",
  "manifest_version": 2,
  "name": "AutoFullscreen",
  "version": "2.0.4",
  "homepage_url": "https://github.com/insiderser/AutoFullscreen",
  "background": {
    "scripts": [
      "startup.js"
    ]
  },
  "icons": {
    "64": "icons/fullscreen_64x64.png",
    "128": "icons/fullscreen_128x128.png"
  },
  "applications": {
    "gecko": {
      "strict_min_version": "48.0"
    }
  }
}