support net45 (#29)

Author: ManniManfred

src/GitLabApiClient/GitLabApiClient.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netstandard2.0</TargetFramework>
+    <TargetFrameworks>netstandard2.0;net45</TargetFrameworks>
     <Version>1.0.0</Version>
     <GeneratePackageOnBuild>false</GeneratePackageOnBuild>
     <AssemblyVersion>1.0.0.0</AssemblyVersion>
@@ -38,4 +38,9 @@
     <PackageReference Include="Newtonsoft.Json" Version="10.0.3" />
   </ItemGroup>
 
+  <ItemGroup Condition="'$(TargetFramework)' == 'net45'">
+    <Reference Include="System.Net.Http" />
+    <Reference Include="System.Web" />
+  </ItemGroup>
+
 </Project>