Examine source code of Toggle darkmode

{
  "description": "Adds a button to enable dark mode",
  "author": "MrOtherGuy",
  "manifest_version": 2,
  "name": "Toggle darkmode",
  "permissions": [
    "browserSettings"
  ],
  "version": "0.2resigned1",
  "background": {
    "scripts": [
      "background-script.js"
    ]
  },
  "browser_action": {
    "default_title": "Toggle Darkmode",
    "browser_style": true
  },
  "applications": {
    "gecko": {
      "id": "toggledarkmode@example.com",
      "strict_min_version": "61.0"
    }
  }
}