Examine source code of MaterialFox Helper

{
  "manifest_version": 2,
  "name": "MaterialFox Helper",
  "version": "1.3resigned1",
  "description": "Provides Material-style themes to accompany the MaterialFox userChrome.css theme.",
  "browser_action": {
    "default_title": "Switch theme",
    "default_popup": "switcher.html",
    "browser_style": true,
    "default_icon": {
      "128": "icon.svg"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "theme",
    "management",
    "storage"
  ],
  "applications": {
    "gecko": {
      "id": "materialfox-helper@mucksponge",
      "strict_min_version": "58.0"
    }
  }
}