Update to ImageSharp 3 (#220)

Author: SimonCropp

src/Directory.Build.props

@@ -2,7 +2,7 @@
 <Project>
   <PropertyGroup>
     <NoWarn>CS1591;CS0649</NoWarn>
-    <Version>2.1.1</Version>
+    <Version>3.0.0</Version>
     <AssemblyVersion>1.0.0</AssemblyVersion>
     <SignAssembly>false</SignAssembly>
     <PackageTags>DocNet, pdf, Verify</PackageTags>

src/Verify.DocNet/Verify.DocNet.csproj

@@ -1,11 +1,11 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFramework>netstandard2.0</TargetFramework>
+    <TargetFramework>net6.0</TargetFramework>
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="Argon" Version="0.4.0" />
     <PackageReference Include="Docnet.Core" Version="2.3.1" />
-    <PackageReference Include="SixLabors.ImageSharp" Version="2.1.3" />
+    <PackageReference Include="SixLabors.ImageSharp" Version="3.0.0" />
     <PackageReference Include="Verify" Version="19.10.0" />
     <PackageReference Include="ProjectDefaults" Version="1.0.87" PrivateAssets="all" />
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.1.1" PrivateAssets="All" Condition="$(Configuration) == 'Release'" />

src/Verify.DocNet/VerifyDocNet_Pdf.cs

@@ -1,8 +1,6 @@
 using Docnet.Core;
 using Docnet.Core.Converters;
 using Docnet.Core.Readers;
-using SixLabors.ImageSharp;
-using SixLabors.ImageSharp.PixelFormats;
 
 namespace VerifyTests;