[Feature]: update license header of all files to use SDPX - makes license header smaller #392

Prerequisites

• I have written a descriptive issue title
• I have verified that I am running the latest version of the SysML2.NET
• I have searched open and closed issues to ensure it has not already been reported

Description

[Feature]: update license header of all files to use SPDX-License-Identifier - makes license header smaller

// ------------------------------------------------------------------------------------------------
//
//
// Copyright (C) 2022-2026 Starion Group S.A.
// SPDX-License-Identifier: Apache-2.0
//
//
// ------------------------------------------------------------------------------------------------