Enable strong name signing

Fixes: #254

Author: hymccord

build/Community.Toolkit.Common.props

@@ -20,6 +20,11 @@
     <Nullable>enable</Nullable>
   </PropertyGroup>
 
+  <PropertyGroup>
+    <SignAssembly>true</SignAssembly>
+    <AssemblyOriginatorKeyFile>$(RepositoryDirectory)toolkit.snk</AssemblyOriginatorKeyFile>
+  </PropertyGroup>
+
   <PropertyGroup>
     <IsTestProject>$(MSBuildProjectName.Contains('Test'))</IsTestProject>
     <IsCoreProject Condition="$(IsTestProject)">False</IsCoreProject>