readme : update links (#27617)

* readme : update links

* readme : update maintainer PRs list

Add the new members of the `ggml-org` `maintainers` team to the
author filter of the maintainer PRs link (nikwen, marty1885,
Titaniumtown), keeping the canonical team ordering. The list now
matches the team exactly (35 members).

Assisted-by: pi:llama.cpp/Qwen3.8-27B