fix: make slider on top of blocks (#244)

Author: Y-k-Y

src/frontend/styles/components/sidebar.pcss

@@ -235,6 +235,7 @@
     border-radius: 8px;
     cursor: pointer;
     background-color: var(--color-link-hover);
+    z-index: 10;
 
     @media (--desktop) {
       display: flex;