Added TreatWarningsAsErrors on release builds

Author: egil

src/Egil.RazorComponents.Testing.Library.csproj

@@ -34,6 +34,10 @@ This library's goal is to make it easy to write comprehensive, stable unit tests
     <IncludeSymbols>true</IncludeSymbols>
     <SymbolPackageFormat>snupkg</SymbolPackageFormat>
   </PropertyGroup>
+
+  <PropertyGroup Condition="'$(Configuration)' == 'Release'">
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
+  </PropertyGroup>
 
   <ItemGroup>
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.0.0" PrivateAssets="All" />