Examine source code of Universal Inbox

{
  "manifest_version": 3,
  "version": "0.1.5",
  "name": "Universal Inbox",
  "description": "Universal Inbox browser extension",
  "icons": {
    "16": "icons/extension_16.png",
    "32": "icons/extension_32.png",
    "48": "icons/extension_48.png",
    "128": "icons/extension_128.png"
  },
  "action": {
    "default_title": "Send page to Universal Inbox"
  },
  "options_ui": {
    "page": "options_ui/page.html",
    "open_in_tab": false
  },
  "background": {
    "service_worker": "background/service_worker.js",
    "scripts": [
      "background/service_worker.js"
    ]
  },
  "permissions": [
    "activeTab",
    "scripting",
    "storage",
    "notifications",
    "cookies",
    "contextualIdentities",
    "webRequest",
    "webRequestBlocking",
    "alarms"
  ],
  "optional_permissions": [
    "https://*/*",
    "http://localhost:8080/*"
  ],
  "optional_host_permissions": [
    "https://*/*",
    "http://localhost/*"
  ],
  "host_permissions": [
    "https://app.universal-inbox.com/*",
    "https://app.slack.com/*",
    "https://*.slack.com/*"
  ],
  "author": "David Rousselie",
  "browser_specific_settings": {
    "gecko": {
      "id": "universal-inbox@universal-inbox.com",
      "strict_min_version": "128.0"
    }
  }
}