Removing support for .net 3.5

Author: Matt Hunt

src/GeoJSON.Net.sln

@@ -5,7 +5,6 @@ VisualStudioVersion = 15.0.26430.6
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{7AFBD129-E5A1-48D0-B7F6-7CCD6D06AF17}"
 	ProjectSection(SolutionItems) = preProject
-		..\GeoJSON.Net.nuspec = ..\GeoJSON.Net.nuspec
 		..\LICENSE.md = ..\LICENSE.md
 		..\README.md = ..\README.md
 	EndProjectSection

src/GeoJSON.Net/GeoJSON.Net.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netstandard1.0;netstandard1.1;netstandard2.0;netstandard2.1;net35;net40;net45;</TargetFrameworks>
+    <TargetFrameworks>netstandard1.0;netstandard1.1;netstandard2.0;netstandard2.1;net40;net45;net6.0</TargetFrameworks>
     <Description>.Net types for the GeoJSON RFC to be used with Json.Net</Description>
     <Authors>Matt Hunt;Joerg Battermann;Xavier Fischer</Authors>
     <Company>GeoJSON.Net</Company>
@@ -17,7 +17,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Newtonsoft.Json" Version="10.0.2" />
+    <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />
   </ItemGroup>
 
   <PropertyGroup>