2917: Fix tts on ios proposal

[steffenkleinle]

Short description

This PR fixes tts on iOS and a few other bugs and problems with tts.
Furthermore, I added some tests and did some refactoring.

Proposed changes

• Fix tts on iOS by removing the listener before stopping/pausing tts
• Allow reading content of 2nd level categories (see discussion here)
• Fix tts sentences when navigating between pages
• Handle opening of player in TtsContainer instead of header for clear responsibilities
• Only initialize tts once actually needed (fixes annoying issues if no tts engine installed)
• Error handling (show users a message if initializing fails)
• Create a new useAppStateListener hook
• Improve tests for TtsContainer and useTtsPlayer
• Further improvements and refactoring

Side effects

N/A, hopefully everything works now on both android and ios.

Testing

Test the tts player thoroughly on both ios and android! Press all buttons multiple times (especially pause, play, previous, next) and navigate between different pages while the tts player is open.

Resolved issues

Fixes: #2917

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[steffenkleinle]

I did not find another way to ensure that the correct sentences are set after navigating back.

[f1sh1918]

Some minor comments. But looks good. 👍
Glad that you found a better solution :)
Tested on ios real device

[LeandraH]

Very cool! Tested on real iOS

[bahaaTuffaha]

Sorry I was late to check it out
Great work...
one thing
You changed something at useTtsPlayer.ts so when I change the language while its speaking the player will be disabled and nothing to read.

(tested on Andorid)