Examine source code of Automatic Fullscreen

{
  "manifest_version": 3,
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "icons": {
    "16": "./icon_16.png",
    "48": "./icon_48.png",
    "128": "./icon_128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "automatic-fullscreen-extension@fredriks"
    }
  },
  "name": "Automatic Fullscreen",
  "description": "Puts a window automatically to fullscreen-mode when the window is opened for the first time.",
  "version": "1.0.6",
  "author": "Fredrik Gundersen",
  "homepage_url": "https://github.com/gundersen-f/automatic-fullscreen-browser-extension#readme"
}