feat: try to implement Aqua.

demo/Ursa.Demo/App.axaml

@@ -3,7 +3,9 @@
     xmlns="https://github.com/avaloniaui"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
     xmlns:u-semi="https://irihi.tech/ursa/themes/semi"
-    xmlns:semi="https://irihi.tech/semi">
+    RequestedThemeVariant="{x:Static semi:SemiTheme.Aquatic}"
+    xmlns:semi="https://irihi.tech/semi"
+    xmlns:demo="clr-namespace:Ursa.Demo">
     <Application.Styles>
         <semi:SemiTheme Locale="zh-CN" />
         <u-semi:SemiTheme Locale="zh-CN" />

demo/Ursa.Demo/Ursa.Demo.csproj

@@ -19,7 +19,9 @@
         <!--Condition below is needed to remove Avalonia.Diagnostics package from build output in Release configuration.-->
         <PackageReference Condition="'$(Configuration)' == 'Debug'" Include="Avalonia.Diagnostics" Version="$(AvaloniaVersion)" />
         <PackageReference Include="CommunityToolkit.Mvvm" Version="8.2.0" />
+        <!--
         <PackageReference Include="Semi.Avalonia" Version="11.1.0.2" />
+        -->
     </ItemGroup>
 
     <ItemGroup>
@@ -30,4 +32,10 @@
     <ItemGroup>
       <Folder Include="Models\" />
     </ItemGroup>
+
+    <ItemGroup>
+      <Reference Include="Semi.Avalonia">
+        <HintPath>Assets\Semi.Avalonia.dll</HintPath>
+      </Reference>
+    </ItemGroup>
 </Project>