[m-rev.] for review: rewrite the MinGW / MSYS / MSYS2 README

[Zoltan Somogyi]

On Fri, 2 Jan 2026 13:41:07 +1100, Julien Fischer <jfischer at opturion.com> wrote:
> In the absence of any review comments I intend to commit this one
> (and do the associated file renaming) later today.

I know nowhere enough about Windows programming to review this,
so if Peter is not available, then commit it now.

Zoltan.