Fix: Fixed alignment of the add tab button (#15194)

Author: yaira2

src/Files.App/Views/MainPage.xaml

@@ -142,13 +142,14 @@
 				TabStripVisibility="Visible"
 				Visibility="Visible">
 				<tabbar:TabBar.FooterElement>
+					<!--  Height is not divisble by four in order to properly align the button  -->
 					<Button
 						x:Name="HorizontalMultitaskingControlAddButton"
-						Width="32"
-						Height="32"
+						Width="30"
+						Height="30"
 						Padding="8"
 						HorizontalAlignment="Left"
-						VerticalAlignment="Bottom"
+						VerticalAlignment="Center"
 						AllowDrop="True"
 						AutomationProperties.Name="{x:Bind Commands.NewTab.AutomationName}"
 						Background="Transparent"