title: Where is ImmutableArray?
body: <p>Why does <a href="https://msdn.microsoft.com/en-us/library/system.collections.immutable.immutablearray%28v=vs.111%29.aspx" rel="noreferrer">ImmutableArray</a> seem to not be there in Microsoft Immutable Collections NuGet package version <a href="https://www.nuget.org/packages/Microsoft.Bcl.Immutable/1.0.34" rel="noreferrer">1.0.34</a>?</p>
  
  <p><img src="https://i.stack.imgur.com/XNbQM.png" alt="enter image description here"></p>