Merge pull request #15 from sharwell/update-readme

Update the readme

Author: sharwell

README.md

@@ -8,14 +8,32 @@ IL weaver for adding nullability annotations to .NET Framework and .NET Standard
 
 [![Join the chat at https://gitter.im/tunnelvisionlabs/ReferenceAssemblyAnnotator](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/tunnelvisionlabs/ReferenceAssemblyAnnotator?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 
+## Requirements
+
+* Build: C# compiler version 3.2 Beta 2 or newer (ships with Visual Studio 2019 version 16.3 Preview 2 and newer). Older
+  versions of the compiler interpret nullable metadata differently, which can lead to incorrect build warnings.
+* Editing experience: Visual Studio 2019 version 16.3 Preview 2 or newer.
+
 ## Usage
 
+### Assemblies included by default
+
+* .NET Framework targets
+    * mscorlib
+* .NET Standard targets
+    * All assemblies which are defined by the .NET Standard
+
+### Example configuration
+
 ```xml
 <PropertyGroup>
   <!-- Specifies the version of this rewriter to use -->
-  <TunnelVisionLabsReferenceAssemblyAnnotatorVersion>1.0.0-alpha.10</TunnelVisionLabsReferenceAssemblyAnnotatorVersion>
+  <TunnelVisionLabsReferenceAssemblyAnnotatorVersion>1.0.0-alpha.31</TunnelVisionLabsReferenceAssemblyAnnotatorVersion>
   <!-- Specifies the version of Microsoft.NETCore.App.Ref to obtain nullability information from -->
   <AnnotatedReferenceAssemblyVersion>3.0.0-preview8-28405-07</AnnotatedReferenceAssemblyVersion>
+  <!-- Includes the nullable attributes from dotnet/coreclr as source code with 'internal' accessibility. Set this to
+       false if the attributes are included from another source and/or are not needed. -->
+  <GenerateNullableAttributes>true</GenerateNullableAttributes>
 </PropertyGroup>
 
 <ItemGroup>
@@ -26,7 +44,6 @@ IL weaver for adding nullability annotations to .NET Framework and .NET Standard
 
 <ItemGroup>
   <!-- Specifies the reference assemblies to rewrite -->
-  <UnannotatedReferenceAssembly Include="mscorlib" />
   <UnannotatedReferenceAssembly Include="System" />
   <UnannotatedReferenceAssembly Include="System.Core" />
 </ItemGroup>