Proj0220: Symbol package format snupkg requires include symbols to be enabled

When creating symbols .snupkg package, not having <IncludeSymbols> set to true will not generate the symbols package at all.

Non-compliant

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>net10.0</TargetFramework>
    <SymbolPackageFormat>snupkg</SymbolPackageFormat>
    <DebugType>portable</DebugType>
  </PropertyGroup>

</Project>

Compliant

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>net10.0</TargetFramework>
    <IncludeSymbols>true</IncludeSymbols>
    <SymbolPackageFormat>snupkg</SymbolPackageFormat>
    <DebugType>portable</DebugType>
  </PropertyGroup>

</Project>