Examine source code of Clipsync

{
  "manifest_version": 2,
  "name": "Clipsync",
  "version": "0.6",
  "description": "Adds clipboard read permissions for Clipsync web in Firefox.",
  "icons": {
    "48": "icon.png",
    "96": "icon.png"
  },
  "permissions": [
    "activeTab",
    "clipboardRead",
    "https://*.clipsync.io/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://*.clipsync.io/*"
      ],
      "js": [
        "clipsync.js"
      ],
      "run_at": "document_start"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{9e300a9a-fdcc-4d9b-9f8b-0a55b511320d}"
    }
  }
}