feat: improve support for configuring http client

Improve support to configure HTTP client when using
Serilog.Settings.Configuration.

Closes #49
Closes #123

src/Serilog.Sinks.Http/Serilog.Sinks.Http.csproj

@@ -29,8 +29,9 @@
     <PackageReference Include="Serilog.Sinks.File" Version="4.1.0" />
     <PackageReference Include="Serilog.Sinks.PeriodicBatching" Version="2.3.0" />
     <PackageReference Include="Serilog.Sinks.RollingFile" Version="3.3.0" />
+    <PackageReference Include="Microsoft.Extensions.Configuration" Version="3.1.6" />
     <!-- SourceLink -->
-    <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.0.0" PrivateAssets="All"/>
+    <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.0.0" PrivateAssets="All" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetFramework)' == 'net45' Or '$(TargetFramework)' == 'net461'">
@@ -44,7 +45,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <None Include="assets\serilog-sink-nuget.png" Pack="true" PackagePath="\"/>
+    <None Include="assets\serilog-sink-nuget.png" Pack="true" PackagePath="\" />
   </ItemGroup>
 
 </Project>