improved dynamic CSS handling

Oqtane.Client/Shared/ThemeBuilder.razor

@@ -1,6 +1,8 @@
 @using Oqtane.Shared
 @using Oqtane.Modules
+@using Microsoft.JSInterop
 @namespace Oqtane.Shared
+@inject IJSRuntime jsRuntime
 
 @DynamicComponent
 
@@ -28,4 +30,12 @@
             }
         };
     }
+
+    protected override async Task OnParametersSetAsync()
+    {
+        // remove any custom CSS
+        var interop = new Interop(jsRuntime);
+        await interop.RemoveCSS("Themes/");
+        await interop.RemoveCSS("Modules/");
+    }
 }