feat: initialize.

src/Ursa.Themes.Semi/Controls/NumericUpDown.axaml

@@ -0,0 +1,12 @@
+<ResourceDictionary xmlns="https://github.com/avaloniaui"
+                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+                    xmlns:u="https://irihi.tech/ursa">
+    <!-- Add Resources Here -->
+    <ControlTheme x:Key="{x:Type u:NumericUpDown}" TargetType="{x:Type u:NumericUpDown}">
+        <Setter Property="Template">
+            <ControlTemplate>
+                <Rectangle Fill="Red" Width="100" Height="100"></Rectangle>
+            </ControlTemplate>
+        </Setter>
+    </ControlTheme>
+</ResourceDictionary>

src/Ursa.Themes.Semi/Controls/_index.axaml

@@ -12,6 +12,7 @@
         <ResourceInclude Source="KeyGestureInput.axaml" />
         <ResourceInclude Source="Loading.axaml" />
         <ResourceInclude Source="Navigation.axaml" />
+        <ResourceInclude Source="NumericUpDown.axaml" />
         <ResourceInclude Source="Pagination.axaml" />
         <ResourceInclude Source="TagInput.axaml" />
         <ResourceInclude Source="Timeline.axaml" />