Extension of Keep-Screen-On feature with a timer

[Palloxin]

Describe your suggested feature

Add an option to let users choose the Timer of when the screen should turn off. Instead of having Always the screen On what about turning the screen off after 3-4 minutes of inactivity?

Why

Sometimes i fall asleep while reading and.. i wake up with 7% battery or with the phone ded so.. i guess many users would prefer this option too.

Other details

https://github.com/LNReader/lnreader/assets/75091899/521f4aed-5d81-4a37-9c86-d47e7b6c8672

To be clear i am not asking to replace Keep Screen On with the timer. Both should exist and selectable.

Make sure the countdown starts everytime the reading mode is accessed by the user; be it from opening a chapter (next chapter, <, >, from "App Overview" (also called "Recent", from the android navigation bar), from history etc..

Note: when i activate, save battery mode and ultra save battery mode the phone will forcefully overwrite the settings related to the countdown like here:

so idk if i continue using it it will be still.be applied.

Acknowledgements

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• [X] I have updated the app to version 1.1.18.
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