Hi, readest is really a great work, it's almost the best book reader I can found. However, there still is one thing can be enhanced.

Does your feature request involve difficulty completing a task? Please describe.
As a user not on the Windows platform and not utilizing Edge, I am unable to access the Text-to-Speech (TTS) functionality. Therefore, I am curious if it would be possible to incorporate support for custom TTS engines?

Describe the solution you'd like
This functionality can be achieved in multiple ways. One approach is to allow users to populate a JSON configuration file that specifies the request URL, the request method, and other similar details. Alternatively, you could provide an open API for plugin developers, enabling them to create plugins for custom TTS (Text-to-Speech) engines.

BTW, there is a new open source TTS engine works very well.