add GifImage doc

src/Shared/HandyControlDemo_Code/HandyControlDemo_Code.csproj

@@ -3,7 +3,7 @@
     <UseWPF>true</UseWPF>
     <AssemblyName>HandyControlDemoCode</AssemblyName>
     <RootNamespace>HandyControlDemoCode</RootNamespace>
-    <TargetFrameworks>netcoreapp3.0;netcoreapp3.1;net40;net45;net462;net47;net48;net50</TargetFrameworks>
+    <TargetFrameworks>netcoreapp3.0;netcoreapp3.1;net40;net45;net462;net47;net48;net5.0</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup>
     <Resource Include="..\..\Shared\HandyControlDemo_Shared\Window\AboutWindow.xaml">

src/Shared/HandyControlDemo_Shared/Window/AboutWindow.xaml.cs

@@ -24,12 +24,12 @@ namespace HandyControlDemo.Window
             var netVersion = "NET 47";
 #elif NET48
             var netVersion = "NET 48";
+#elif NET5_0
+            var netVersion = "NET 50";
 #elif NETCOREAPP3_0
             var netVersion = "CORE 30";
 #elif NETCOREAPP3_1
             var netVersion = "CORE 31";
-#else
-            var netVersion = "NET 50";
 #endif
             Version = $"v {versionInfo.FileVersion} {netVersion}";
         }