Bump .NET core version

Author: kthompson

src/Envelop/Envelop.csproj

@@ -1,11 +1,12 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;net452;net462</TargetFrameworks>
+    <TargetFrameworks>net452;net462;net472;net48;netstandard2.0;netstandard2.1</TargetFrameworks>
+    <LangVersion>8</LangVersion>
   </PropertyGroup>
 
   <PropertyGroup>
-    <VersionPrefix>0.2.0</VersionPrefix>
+    <VersionPrefix>0.3.0</VersionPrefix>
 
     <Description>Envelop is a simple to use Dependency Injection and Inversion of Control container</Description>
     <PackageId>Envelop</PackageId>

tests/Envelop.Tests/Envelop.Tests.csproj

@@ -1,9 +1,11 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netcoreapp2.0</TargetFramework>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
 
     <IsPackable>false</IsPackable>
+
+    <LangVersion>8</LangVersion>
   </PropertyGroup>
 
   <ItemGroup>