feat(Step): add CurrentStepIndex property (#6316)

* feat(Step): add 'CurrentStepIndex' to obtain the real-time value of _currentStepIndex

* test: 增加单元测试

---------

Co-authored-by: Argo Zhang <[email protected]>

Author: momijijin

src/BootstrapBlazor/Components/Step/Step.razor.cs

@@ -53,6 +53,11 @@ public partial class Step
 
     private int _currentStepIndex;
 
+    /// <summary>
+    /// 获得当前步骤索引（只读）
+    /// </summary>
+    public int CurrentStepIndex => _currentStepIndex;
+
     /// <summary>
     /// 获得 组件样式字符串
     /// </summary>

test/UnitTest/Components/StepTest.cs

@@ -37,6 +37,8 @@ public void Step_Items()
 
         body = cut.FindAll(".step-body-item");
         Assert.Empty(body);
+
+        Assert.Equal(0, cut.Instance.CurrentStepIndex);
     }
 
     [Fact]