The extension talks to one service: the Transcrib Si API. The key stays in the browser profile of
this extension and is sent in the X-API-Key header of the request and nowhere else.
The address of the service. The default is https://api.transcrib.si. A local address
(http://127.0.0.1:8090) can be used for the tests.
The key is created in the web app: https://transcrib.si/app.html → API keys. The service
shows the full key only once. The extension works without a key too: paste the access token of the
account instead.
Sent as Authorization: Bearer. The key wins when both are filled.
The link to the web app in the popup opens this address.