feat: add net6.0 target framework

Author: phnx47

src/Prometheus.Client.MetricServer.csproj

@@ -1,8 +1,8 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <Description>Standalone Kestrel server for the Prometheus.Client</Description>
-    <VersionPrefix>4.3.1</VersionPrefix>
-    <TargetFrameworks>netstandard2.0;netstandard2.1;netcoreapp3.1;net5.0</TargetFrameworks>
+    <VersionPrefix>4.4.0</VersionPrefix>
+    <TargetFrameworks>netstandard2.0;netstandard2.1;netcoreapp3.1;net5.0;net6.0</TargetFrameworks>
     <PackageId>Prometheus.Client.MetricServer</PackageId>
     <RepositoryUrl>https://github.com/prom-client-net/prom-client-metricserver</RepositoryUrl>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
@@ -14,7 +14,7 @@
   <ItemGroup>
     <PackageReference Include="Prometheus.Client" Version="[4.5.3,5.0.0)" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetFramework)' == 'netcoreapp3.1' OR '$(TargetFramework)' == 'net5.0'">
+  <ItemGroup Condition="'$(TargetFramework)' == 'netcoreapp3.1' OR '$(TargetFramework)' == 'net5.0' OR '$(TargetFramework)' == 'net6.0'">
     <FrameworkReference Include="Microsoft.AspNetCore.App" />
   </ItemGroup>
   <ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0' OR '$(TargetFramework)' == 'netstandard2.1'">

tests/Prometheus.Client.MetricServer.Tests.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <TargetFramework>net6.0</TargetFramework>
     <IsPackable>false</IsPackable>
     <SignAssembly>true</SignAssembly>
     <AssemblyOriginatorKeyFile>../Prometheus.Client.MetricServer.snk</AssemblyOriginatorKeyFile>