Examples - Add .Net 5.0 and conditionally .Net 6.0 as target frameworks

- .Net 6.0 requires VS2022

This may need to be changed if Appveyor doesn't like building the .Net 5.0 targets

Author: amaitland

CefSharp.OffScreen.Example/CefSharp.OffScreen.Example.netcore.csproj

@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <Project>
     <!-- Note: We cannot use the recommended style of specifying <Project Sdk=...> because we need
        to set BaseIntermediateOutputPath and BaseOutputPath before the SDK props are imported. -->
@@ -11,7 +11,8 @@
 
     <PropertyGroup>
         <OutputType>Exe</OutputType>
-        <TargetFramework>netcoreapp3.1</TargetFramework>
+        <TargetFrameworks>netcoreapp3.1;net5.0-windows</TargetFrameworks>
+        <TargetFrameworks Condition="'$(VisualStudioVersion)'=='17.0'">$(TargetFrameworks);net6.0-windows</TargetFrameworks>
         <RootNamespace>CefSharp.OffScreen.Example</RootNamespace>
         <AssemblyName>CefSharp.OffScreen.Example</AssemblyName>
         <GenerateAssemblyInfo>false</GenerateAssemblyInfo>

CefSharp.WinForms.Example/CefSharp.WinForms.Example.netcore.csproj

@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <Project>
     <!-- Note: We cannot use the recommended style of specifying <Project Sdk=...> because we need
        to set BaseIntermediateOutputPath and BaseOutputPath before the SDK props are imported. -->
@@ -11,7 +11,8 @@
 
     <PropertyGroup>
         <OutputType>WinExe</OutputType>
-        <TargetFramework>netcoreapp3.1</TargetFramework>
+        <TargetFrameworks>netcoreapp3.1;net5.0-windows</TargetFrameworks>
+        <TargetFrameworks Condition="'$(VisualStudioVersion)'=='17.0'">$(TargetFrameworks);net6.0-windows</TargetFrameworks>
         <RootNamespace>CefSharp.WinForms.Example</RootNamespace>
         <AssemblyName>CefSharp.WinForms.Example</AssemblyName>
         <UseWindowsForms>true</UseWindowsForms>

CefSharp.Wpf/CefSharp.Wpf.netcore.csproj

@@ -10,7 +10,8 @@
   <Import Project="Sdk.props" Sdk="Microsoft.NET.Sdk.WindowsDesktop" />
 
   <PropertyGroup>
-    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <TargetFrameworks>netcoreapp3.1;net5.0-windows</TargetFrameworks>
+    <TargetFrameworks Condition="'$(VisualStudioVersion)'=='17.0'">$(TargetFrameworks);net6.0-windows</TargetFrameworks>
     <RootNamespace>CefSharp.Wpf</RootNamespace>
     <AssemblyName>CefSharp.Wpf</AssemblyName>
     <DocumentationFile>$(BaseOutputPath)$(PlatformTarget)\$(Configuration)\$(TargetFramework)\$(AssemblyName).xml</DocumentationFile>