add net47 tfm

Author: phnx47

src/Prometheus.Client.Abstractions/Prometheus.Client.Abstractions.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <RootNamespace>Prometheus.Client</RootNamespace>
-    <TargetFrameworks>net462;netstandard2.0;net6.0</TargetFrameworks>
+    <TargetFrameworks>net462;net47;netstandard2.0;net6.0</TargetFrameworks>
     <Description>Abstractions for Prometheus.Client</Description>
     <RepositoryUrl>https://github.com/prom-client-net/prom-client</RepositoryUrl>
   </PropertyGroup>

src/Prometheus.Client/Prometheus.Client.csproj

@@ -1,10 +1,10 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>net462;netstandard2.0;net6.0</TargetFrameworks>
+    <TargetFrameworks>net462;net47;netstandard2.0;net6.0</TargetFrameworks>
     <Description>.NET client for Prometheus</Description>
     <RepositoryUrl>https://github.com/prom-client-net/prom-client</RepositoryUrl>
   </PropertyGroup>
-  <ItemGroup Condition="'$(TargetFramework)' == 'net462' OR '$(TargetFramework)' == 'netstandard2.0'">
+  <ItemGroup Condition="'$(TargetFramework)' == 'net462' OR '$(TargetFramework)' == 'net47' OR '$(TargetFramework)' == 'netstandard2.0'">
     <PackageReference Include="System.Memory" Version="4.6.3" />
   </ItemGroup>
   <ItemGroup>