Rewrite hex encoder/decoder

Emby.Drawing/Emby.Drawing.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netstandard2.0</TargetFramework>
+    <TargetFramework>netstandard2.1</TargetFramework>
     <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
@@ -17,9 +17,4 @@
     <Compile Include="..\SharedVersion.cs" />
   </ItemGroup>
 
-  <PropertyGroup>
-      <!-- We need at least C# 7.1 for the "default literal" feature-->
-    <LangVersion>latest</LangVersion>
-  </PropertyGroup>
-
 </Project>