## Summary
* **What is the goal of this PR?**
* This PR adds a setting to (additionally) map the forward page turn
onto the powerbutton when in `EPUBReaderActivity` and powerbutton short
press is not mapped to sleep mode. I find the powerbutton to be exactly
where my thumb is while reading so it is very convenient to map the
forwardpage turn to that. Maybe Im not alone with this ^^
* **What changes are included?**
## Additional Context
* Add any other information that might be helpful for the reviewer
(e.g., performance implications, potential risks, specific areas to
focus on).
97c4871316