feat: add keyboard shortcut to toggle sidebar

Author: hirehamir

src/front-end/js/book.js

@@ -593,6 +593,20 @@ aria-label="Show hidden lines"></button>';
         window.removeEventListener('mouseup', stopResize, false);
     }
 
+      // Add Ctrl + Shift + S as a shortcut to toggle the sidebar.
+    document.addEventListener("keydown", function (event) {
+        if (event.ctrlKey && event.shiftKey && event.key === "S") {
+            event.preventDefault();
+            if (sidebarToggleAnchor.checked) {
+                sidebarToggleAnchor.checked = false;
+                hideSidebar();
+            } else {
+                sidebarToggleAnchor.checked = true;
+                showSidebar();
+            }
+        }
+    });
+
     document.addEventListener('touchstart', function(e) {
         firstContact = {
             x: e.touches[0].clientX,