fix: vulnerability

Author: phnx47

src/Prometheus.Client.MetricServer/Prometheus.Client.MetricServer.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <Description>Standalone Kestrel server for the Prometheus.Client</Description>
-    <VersionPrefix>4.3.0</VersionPrefix>
+    <VersionPrefix>4.3.1</VersionPrefix>
     <TargetFrameworks>netstandard2.0;netstandard2.1;netcoreapp3.1;net5.0</TargetFrameworks>
     <AssemblyName>Prometheus.Client.MetricServer</AssemblyName>
     <PackageId>Prometheus.Client.MetricServer</PackageId>
@@ -33,6 +33,7 @@
     <FrameworkReference Include="Microsoft.AspNetCore.App" />
   </ItemGroup>
   <ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0' OR '$(TargetFramework)' == 'netstandard2.1'">
+    <PackageReference Include="System.Text.Encodings.Web" Version="4.5.1" />
     <PackageReference Include="Microsoft.AspNetCore.Server.Kestrel" Version="2.2.0" />
     <PackageReference Include="Microsoft.AspNetCore.Server.Kestrel.Https" Version="2.2.0" />
   </ItemGroup>