refactor: 增加样式

Author: ArgoZhang

src/BootstrapBlazor/Components/Select/Select.razor.scss

@@ -121,7 +121,8 @@
     transform: rotate(0);
 }
 
-.select {
+.select,
+.auto-complete {
     .clear-icon {
         position: absolute;
         height: 100%;

src/BootstrapBlazor/Components/Select/SelectBase.cs

@@ -204,7 +204,7 @@ protected override void OnParametersSet()
     private bool IsNullable() => !ValueType.IsValueType || NullableUnderlyingType != null;
 
     /// <summary>
-    /// 
+    /// Gets whether show the clear button.
     /// </summary>
     /// <returns></returns>
     protected bool GetClearable() => IsClearable && !IsDisabled && IsNullable();