Examine source code of Sync Theme

{
  "manifest_version": 3,
  "name": "Sync Theme",
  "version": "1.0.0",
  "description": "Switches Gmail, Grafana, and Slack between light and dark to match your system theme. Works only on those sites.",
  "icons": {
    "16": "icons/icon-16.png",
    "32": "icons/icon-32.png",
    "48": "icons/icon-48.png",
    "128": "icons/icon-128.png"
  },
  "action": {
    "default_title": "Sync Theme",
    "default_popup": "src/popup/popup.html",
    "default_icon": {
      "16": "icons/icon-16.png",
      "32": "icons/icon-32.png"
    }
  },
  "options_ui": {
    "page": "src/options/options.html",
    "open_in_tab": true
  },
  "background": {
    "scripts": [
      "src/background/service-worker.js"
    ],
    "type": "module"
  },
  "permissions": [
    "storage",
    "scripting"
  ],
  "optional_host_permissions": [
    "https://*/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://*.grafana.com/*",
        "https://*.grafana.net/*",
        "https://*.slack.com/*",
        "https://grafana.com/*",
        "https://mail.google.com/*",
        "https://slack.com/*"
      ],
      "js": [
        "src/content/bootstrap.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "web_accessible_resources": [
    {
      "resources": [
        "src/content/*.js",
        "src/content/sites/*.js",
        "src/lib/*.js"
      ],
      "matches": [
        "https://*/*"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "sync-theme@sideprojects-dee",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    },
    "gecko_android": {
      "strict_min_version": "142.0"
    }
  }
}