Add package for netstandart2.0

Author: YegorStepanov

src/BenchmarkDotNet/BenchmarkDotNet.csproj

@@ -32,6 +32,9 @@
   <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard2.0' ">
     <PackageReference Include="System.Numerics.Vectors" Version="4.5.0" />
     <PackageReference Include="Microsoft.Win32.Registry" Version="5.0.0" />
+    <PackageReference Include="Microsoft.Bcl.HashCode" Version="1.1.1">
+      <PrivateAssets>all</PrivateAssets>
+    </PackageReference>
   </ItemGroup>
   <ItemGroup Condition="'$(OS)' == 'Windows_NT'">
     <ProjectReference Include="..\BenchmarkDotNet.Disassembler.x64\BenchmarkDotNet.Disassembler.x64.csproj">