Add Text To Speech support (TTS)

This should come after #1293

This issue is about leveraging the TTS support introduced in more recent versions of Godot on desktop and, if possible, using the [speech synthesis](https://developer.mozilla.org/en-US/docs/Web/API/SpeechSynthesis) APIs on the web.

This needs UI/UX design before implementation. Requirements:

- Users should be able to select the voice they desire and this should be stored in their save data. This means we should query all the available TTS voices provided by the platform.
- If users have any system or browser settings for speech speed and other parameters that we can query, we should account for them.
- We should provide a command and perhaps a context menu option to read selected text.
- This may need a different implementation on the web compared to desktop, from what I read on the web the engine feature does not work out of the box currently (to be verified). The web platform provides an API we can use though.