doc(Scroll): update sidebar style (dotnetcore#2924)

* doc: 滚动条兼容老牌浏览器

* refactor: 微调 Sidebar 位置

* refactor: 更新 Sidebar 圆角样式

Author: ArgoZhang

src/BootstrapBlazor.Server/Components/Layout/NavMenu.razor.css

@@ -29,7 +29,7 @@
     width: 1px;
     position: absolute;
     top: 0;
-    right: 0;
+    right: -1px;
     bottom: 0;
     background-color: var(--bs-border-color);
 }
@@ -39,6 +39,7 @@
         inset: 0px -2px;
         cursor: col-resize;
         background-color: transparent;
+        border-radius: 4px;
     }
 
         .sidebar-bar .sidebar-body:hover {

src/BootstrapBlazor.Server/wwwroot/css/site.css

@@ -290,3 +290,10 @@ code {
         margin: 2rem;
     }
 }
+
+@supports not selector(::-webkit-scrollbar) {
+    .scroll {
+        scrollbar-color: rgba(0,0,0,0.3) rgba(0,0,0,0);
+        scrollbar-width: thin;
+    }
+}