Examine source code of Dark Mode for Outlook

{
  "name": "__MSG_extensionName__",
  "short_name": "__MSG_extensionShortName__",
  "description": "__MSG_extensionDescription__",
  "version": "3.6",
  "default_locale": "en",
  "icons": {
    "16": "img/16.png",
    "32": "img/32.png",
    "48": "img/48.png",
    "64": "img/64.png",
    "128": "img/128.png"
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": false
  },
  "content_scripts": [
    {
      "matches": [
        "*://outlook.live.com/*",
        "*://outlook.office.com/*",
        "*://outlook.office365.com/*",
        "*://support.office.live.com/*"
      ],
      "css": [
        "css/main.css"
      ],
      "js": [
        "js/content.js"
      ],
      "run_at": "document_start"
    },
    {
      "matches": [
        "*://support.office.live.com/*"
      ],
      "css": [
        "css/help.css"
      ],
      "run_at": "document_start",
      "all_frames": true
    }
  ],
  "background": {
    "scripts": [
      "js/background.js"
    ],
    "persistent": true
  },
  "permissions": [
    "storage"
  ],
  "optional_permissions": [
    "tabs",
    "*://*/"
  ],
  "web_accessible_resources": [
    "css/compose.css"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{cf211314-517c-470f-a589-02a4b272f7d5}"
    }
  },
  "manifest_version": 2
}