Add check octicon for merge status

Author: donokuda

src/GitHub.VisualStudio/UI/Views/PullRequestCreationView.xaml

@@ -377,6 +377,7 @@
                 <ui:GitHubActionLink x:Name="branchSelectionButton" Content="master" HasDropDown="True" Margin="5,0,0,0" VerticalAlignment="Center" Click="branchSelectionButton_Click" />
                 <ui:OcticonImage Height="13" Icon="chevron_left" Foreground="{DynamicResource GitHubVsGrayText}" Margin="0,1,0,0"  VerticalAlignment="Center" />
                 <Label Content="{Binding CurrentBranchName}" Foreground="{DynamicResource GitHubVsToolWindowText}"/>
+                <ui:OcticonImage Icon="check" Foreground="Green" HorizontalAlignment="Right"/>
                 <Popup
                     x:Name="branchPopup"
                     AllowsTransparency="True"