SPDX: recognise doxygen `@copyright` command

[JordanYates]

Summary

Doxygen has a command for specifying copyright on a file, @copyright: https://www.doxygen.nl/manual/commands.html#cmdcopyright.
The SPDX generation currently does not recognise this.
For example, cartesian.c:

/**
 * @file
 * @copyright 2024 Embeint Holdings Pty Ltd
 * @author Jordan Yates <jordan@embeint.com>
 *
 * SPDX-License-Identifier: FSL-1.1-ALv2
 */

Generated SPDX:

FileName: ./lib/math/cartesian.c
SPDXID: SPDXRef-File-cartesian.c
FileChecksum: SHA1: 87ed4a1f09a9b8c516a690f07ba86ff07728ac75
FileChecksum: SHA256: e8d83d2d3672ff92622477fe3bc62ad305a2c497a40ad64230cff98c63fd0684
LicenseConcluded: FSL-1.1-ALv2
LicenseInfoInFile: FSL-1.1-ALv2
FileCopyrightText: NOASSERTION

Describe the solution you'd like

SPDX files including copyright information specified using the doxygen syntax.

Alternatives

No response

Additional Context

No response

[JarmouniA]

There is SPDX-FileCopyrightText FYI.