Add sidebar styling and logo documentation link

- Introduced custom scrollbar styles for the sidebar content.
- Added a logo with a "Docs" label for better navigation clarity.

Author: nahoc

style.css

@@ -0,0 +1,34 @@
+#sidebar-content::-webkit-scrollbar {
+  width: 8px;
+}
+
+#sidebar-content::-webkit-scrollbar-track {
+  background: rgba(0, 0, 0, 0.05);
+}
+
+#sidebar-content::-webkit-scrollbar-thumb {
+  background: rgba(0, 0, 0, 0.3);
+  border-radius: 4px;
+}
+
+#sidebar-content::-webkit-scrollbar-thumb:hover {
+  background: rgba(0, 0, 0, 0.5);
+}
+
+.nav-logo {
+  max-width: 160px;
+}
+
+a:has(> .nav-logo)::after {
+  content: "Docs";
+  position: absolute;
+  bottom: 4px;
+  display: block;
+  font-size: 12px;
+  color: rgb(var(--gray-600));
+  left: 36px
+}
+
+.dark a:has(> .nav-logo)::after {
+  color: rgb(var(--gray-400));
+}