Examine source code of Containers Theme

{
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "cookies",
    "storage",
    "theme",
    "contextualIdentities",
    "<all_urls>",
    "tabs"
  ],
  "applications": {
    "gecko": {
      "strict_min_version": "57.0a1",
      "id": "{69c84059-c632-41d0-b3bf-ae54aacb632e}"
    }
  },
  "icons": {
    "96": "img/containers.svg"
  },
  "description": "Change theme colour based on your container color",
  "manifest_version": 2,
  "name": "Containers theme",
  "version": "1.0.4"
}