Examine source code of Rainbow Nightlight

{
  "manifest_version": 2,
  "name": "Rainbow Nightlight",
  "version": "0.1",
  "applications": {
    "gecko": {
      "strict_min_version": "57.0"
    }
  },
  "icons": {
    "16": "rbnl.png",
    "48": "rbnl.png",
    "96": "rbnl.png",
    "128": "rbnl.png"
  },
  "permissions": [
    "alarms",
    "theme"
  ],
  "background": {
    "scripts": [
      "rbnl.js"
    ]
  },
  "default_locale": "en"
}