chore: Add net8.0 as a build target, as its the latest LTS version (#222)

Signed-off-by: Ryan Mattson <[email protected]>

Author: Ryan Mattson

build/Common.prod.props

@@ -9,7 +9,7 @@
   </PropertyGroup>
 
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;net462;net5.0;net6.0;net7.0</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0;net462;net5.0;net6.0;net7.0;net8.0</TargetFrameworks>
     <RepositoryType>git</RepositoryType>
     <RepositoryUrl>https://github.com/open-feature/dotnet-sdk-contrib</RepositoryUrl>
     <Description>OpenFeature is an open specification that provides a vendor-agnostic, community-driven API for feature flagging that works with your favorite feature flag management tool or in-house solution.</Description>