In commit 2f852580fb (CONTRIBUTORS: Improve formatting of per-contributor hyperlinks, 2025-03-02) we accidentally added `mailto:` on a few URLs that should use `https://` instead. Reported-by: Rolf Eike Beer <eb@emlix.com>
2f852580fb
It is more conventional to list contributors in a dedicated file. Also drop the long out-of-date sponsorship section.