Add .net8.0 to target frameworks.

Author: StringEpsilon

PhpSerializerNET.Test/PhpSerializerNET.Test.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
 	<PropertyGroup>
-		<TargetFramework>net7.0</TargetFramework>
+		<TargetFrameworks>net7.0;net8.0</TargetFrameworks>
 		<IsPackable>false</IsPackable>
 	</PropertyGroup>
 	<ItemGroup>

PhpSerializerNET/PhpSerializerNET.csproj

@@ -1,9 +1,9 @@
 <Project Sdk="Microsoft.NET.Sdk">
 	<PropertyGroup>
 		<Title>PhpSerializerNET</Title>
-		<TargetFrameworks>net6.0;net7.0</TargetFrameworks>
+		<TargetFrameworks>net6.0;net7.0;net8.0</TargetFrameworks>
 		<LangVersion>10.0</LangVersion>
-		<Version>1.3.0</Version>
+		<Version>1.4.0</Version>
 		<Authors>StringEpsilon</Authors>
 		<Summary>A library for working with the PHP serialization format.</Summary>
 		<PackageTags>php-serialization, php-serializer, php-deserializer</PackageTags>