fix: webview resetting when reader settings change

[Ecasept]

Previously, changing the reader state caused the whole webview to be rerendered. This resulted in buggy behavior where the TTS would restart from the beginning and scrolling progress would be reverted.

This PR fixes this by manually running Javascript inside the webview when settings change.

Improvements:

• Changing the reader settings will not trigger a reset anymore
• Changing the TTS settings will correctly restart the tts reader.

Implementation:

• The reader state is stored seprately:
  • The initial state is memoized for the initial render, and subsequent changes to the settings will directly update the webview as javascript, instead of triggering a rerender
  • The parts outside of the JSX block can still use the reactive reader settings
• The TTS now verifies that the tts settings actually changed before restarting itself

Limitations:

• Updated custom js will not be executed until the next chapter loads due to browser limitations. I don't think this matters as you can't change custom js from the bottom sheet either way.

Fixes: #1840