bug: Fix the license inconsistency in the files

[mayankjobanputra]

Currently, in the majority of the files, I see these lines. @masci pointed out we should make it consistent with the actual license.

# SPDX-FileCopyrightText: 2023-present U.N. Owen <void@some.where>
#
# SPDX-License-Identifier: MIT

[ZanSara]

Fixed temporarily in #14, I wish there was a working pre-commit hook for this...

[mayankjobanputra]

The issue seems to be fixed, closing this :)