Book Polishing (#639)

* Downgraded ExCSS, the new version has a regression that breaks toCss().

* Cleaned up the next/prev disabling to work more reliably.

Fixed an issue with double arrow on next not disappearing after hitting last page then going back one page.

* Cleaned up some css padding on the side nav progress bar

* Remove the ability to save

* Updated colors of nav bar and side drawer to be darker to separate them from the reader

* Fixed a missed element

* Removed dead code

* Removed TODO, it can't be changed

* Refactored bookmarking on the book progress to have pinpoint accuracy for remembering scroll position. Now will choose the top line on the page.

* Fixed a style issue when applying dark mode from light mode in book reader

UI/Web/src/app/shared/_services/utility.service.ts

@@ -127,4 +127,14 @@ export class UtilityService {
     return Breakpoint.Desktop;
   }
 
+  isInViewport(element: Element, additionalTopOffset: number = 0) {
+    const rect = element.getBoundingClientRect();
+    return (
+        rect.top >= additionalTopOffset &&
+        rect.left >= 0 &&
+        rect.bottom <= (window.innerHeight || document.documentElement.clientHeight) &&
+        rect.right <= (window.innerWidth || document.documentElement.clientWidth)
+    );
+  }
+
 }