Update AdditionalAttributes to nullable; fix docs section order

Changed AdditionalAttributes to nullable in base components for Blazor convention compliance. Cleaned up Grid documentation by removing duplicate and misplaced "GridColumn Parameters" sections and improving order.

Author: gvreddy04

BlazorBootstrap.Demo.RCL/Components/Pages/Docs/Grid/Grid_Doc_01_Documentation.razor

@@ -26,10 +26,6 @@
     <DocxTable TItem="Grid<object>" DocType="DocType.Events" />
 </Section>
 
-<Section Class="p-0" Size="HeadingSize.H3" Name="GridColumn Parameters" PageUrl="@pageUrl" Link="grid-column-parameters">
-    <DocxTable TItem="GridColumn<object>" DocType="DocType.Parameters" />
-</Section>
-
 <Section Class="p-0" Size="HeadingSize.H3" Name="GridColumns Parameters" PageUrl="@pageUrl" Link="grid-columns-parameters">
     <DocxTable TItem="GridColumns" DocType="DocType.Parameters" />
 </Section>

blazorbootstrap/Components/Core/BlazorBootstrapComponentBase.cs

@@ -148,7 +148,7 @@ protected virtual ValueTask DisposeAsyncCore(bool disposing)
     [Description("Gets or sets additional attributes that will be applied to the component.")]
     [ParameterTypeName("Dictionary<string, object>")]
     [Parameter(CaptureUnmatchedValues = true)]
-    public Dictionary<string, object> AdditionalAttributes { get; set; } = default!;
+    public Dictionary<string, object>? AdditionalAttributes { get; set; }
 
     /// <summary>
     /// Gets or sets the CSS class name(s) to apply to the component.

blazorbootstrap/Components/Core/BlazorBootstrapLayoutComponentBase.cs

@@ -141,7 +141,7 @@ protected virtual ValueTask DisposeAsyncCore(bool disposing)
     [Description("Gets or sets additional attributes that will be applied to the component.")]
     [Parameter(CaptureUnmatchedValues = true)]
     [ParameterTypeName("Dictionary<string, object>")]
-    public Dictionary<string, object> AdditionalAttributes { get; set; } = default!;
+    public Dictionary<string, object>? AdditionalAttributes { get; set; }
 
     /// <summary>
     /// Gets or sets the CSS class name(s) to apply to the component.