Add "auto" progress bar position

Automatically choose the progress bar position based on the available space.
Previously it was only possible to automatically switch from a horizontal to a vertical position but not the other way around

src/modules/reader/components/overlay/progress-bar/variants/MobileReaderProgressBar.tsx

@@ -41,6 +41,8 @@ const PROGRESS_BAR_POSITION_TO_SLIDE_DIRECTION: Record<ProgressBarPosition, Slid
     [ProgressBarPosition.BOTTOM]: 'up',
     [ProgressBarPosition.LEFT]: 'right',
     [ProgressBarPosition.RIGHT]: 'left',
+    // should never get accessed
+    [ProgressBarPosition.AUTO]: 'left',
 };
 
 const BaseMobileReaderProgressBar = ({