补充SelectSearchMetadata对象中OnSearchTextChanged

补充SelectSearchMetadata对象中新增ShowSearch属性后，漏掉与之对应的OnSearchTextChanged回调，同时增加ItemTemplate属性，以便个性化下拉显示

Author: Tony-ST0754

src/BootstrapBlazor/Components/Searches/SelectSearchMetadata.cs

@@ -17,6 +17,18 @@ public class SelectSearchMetadata : StringSearchMetadata
     /// </summary>
     public bool ShowSearch { get; set; }
 
+    /// <summary>
+    /// <para lang="zh">获得/设置 搜索文本改变时的回调方法</para>
+    /// <para lang="en">Gets or sets the callback method when the search text changes</para>
+    /// </summary>
+    public Func<string, IEnumerable<SelectedItem>>? OnSearchTextChanged { get; set; }
+
+    /// <summary>
+    /// <para lang="zh">获得/设置 项目模板</para>
+    /// <para lang="en">Gets or sets the item template</para>
+    /// </summary>
+    public RenderFragment<SelectedItem>? ItemTemplate { get; set; }
+
     /// <summary>
     /// <para lang="zh">获得/设置 选择项集合</para>
     /// <para lang="en">Gets or sets the collection of select items</para>

src/BootstrapBlazor/Extensions/ISearchItemExtensions.cs

@@ -161,6 +161,7 @@ private void AddSelectSearchComponent(ISearchItem item, SelectSearchMetadata sel
             builder.AddAttribute(70, nameof(Select<>.PlaceHolder), selectSearchMetadata.PlaceHolder);
             builder.AddAttribute(80, nameof(Select<>.SkipValidate), true);
             builder.AddAttribute(90, nameof(Select<>.ShowSearch), selectSearchMetadata.ShowSearch);
+            builder.AddAttribute(100, nameof(Select<>.OnSearchTextChanged), selectSearchMetadata.OnSearchTextChanged);
             builder.CloseComponent();
         }