Refactor .Net example project (#1049)

Co-authored-by: 东风破 <birdfishs@163.com>

dotnet-examples/Common/Common.csproj

@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>net6.0</TargetFramework>
+        <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+        <RestoreSources>/tmp/packages;$(RestoreSources);https://api.nuget.org/v3/index.json</RestoreSources>
+    </PropertyGroup>
+    <ItemGroup>
+        <PackageReference Include="CommandLineParser" Version="2.9.1" />
+        <PackageReference Include="org.k2fsa.sherpa.onnx" Version="1.10.1" />
+    </ItemGroup>
+
+</Project>