added description for the projects we just added recently

Author: kerryjiang

src/SuperSocket.Kestrel/SuperSocket.Kestrel.csproj

@@ -1,6 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFrameworks>net6.0;net7.0;net8.0</TargetFrameworks>
+    <Description>SuperSocket library allows users to take advantage of Kestrel's high performance socket pipeline.</Description>
   </PropertyGroup>
   <ItemGroup>
     <ProjectReference Include="../SuperSocket.Connection/SuperSocket.Connection.csproj" />

src/SuperSocket.Server.Abstractions/SuperSocket.Server.Abstractions.csproj

@@ -1,4 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <Description>SuperSocket library for server abstractions. It includes many interfaces and base implementation of SuperSocket server components. Users can extend server side base on this project.</Description>
+  </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="Microsoft.Extensions.Hosting.Abstractions" Version="$(MSExtensionsVersion)" />
   </ItemGroup>