.NET Core 3.1 support

https://docs.microsoft.com/en-us/dotnet/core/porting/winforms-breaking-changes

.NET Core 3.1 removed obsolete controls, so 1.x releases of this library triggers runtime exceptions,

System.TypeLoadException
  HResult=0x80131522
  Message=Could not load type 'System.Windows.Forms.ToolBarButton' from assembly 'System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'.
  Source=Crad.Windows.Forms.Actions
  StackTrace:
   at Crad.Windows.Forms.Actions.Action.AddHandler(Component extendee)
   at Crad.Windows.Forms.Actions.Action.InternalAddTarget(Component extendee)
   at Crad.Windows.Forms.Actions.ActionList.SetAction(Component extendee, Action action)
   at JexusManager.MainForm.InitializeComponent() in F:\JexusManager\JexusManager\MainForm.Designer.cs:line 344
   at JexusManager.MainForm..ctor(List`1 files) in F:\JexusManager\JexusManager\MainForm.cs:line 76
   at JexusManager.Program.Main(String[] args) in F:\JexusManager\JexusManager\Program.cs:line 87

Start with the linked .NET Core 3.1 Windows Forms breaking-changes documentation, then inspect Action.AddHandler and the related stack-trace path. Reproduce the TypeLoadException on .NET Core 3.1 and identify the compatibility work needed so the library loads without referencing the removed ToolBarButton type.