style: add dark mode scrollbar styles

Author: woeoio

docs/_sass/custom/custom.scss

@@ -1,3 +1,38 @@
 .site-logo {
   padding-right: 3rem;
 }
+
+/* Dark mode scrollbar styles */
+html.dark-mode {
+  /* WebKit browsers (Chrome, Safari, Edge) */
+  ::-webkit-scrollbar {
+    width: 10px;
+    height: 10px;
+  }
+
+  ::-webkit-scrollbar-track {
+    background: #1a1a1a;
+  }
+
+  ::-webkit-scrollbar-thumb {
+    background: #404040;
+    border-radius: 5px;
+  }
+
+  ::-webkit-scrollbar-thumb:hover {
+    background: #505050;
+  }
+
+  ::-webkit-scrollbar-corner {
+    background: #1a1a1a;
+  }
+}
+
+/* Firefox scrollbar styles */
+@supports (scrollbar-width: thin) {
+  html.dark-mode {
+    scrollbar-color: #404040 #1a1a1a;
+    scrollbar-width: thin;
+  }
+}
+