add initial draft of 4 fun challenge solutions

Changed `bin/new-challenge-md.sh` so that the declaration that
the fun challenge is **OPEN** or **CLOSED** comes first in each section.

Improve punctuation around use of "i.e.,", and "e.g.," in `faq.md`.

Update `bin/new-challenge-md.sh` VERSION to "2.0.1 2026-06-16"

In `2025/challenge.md`, added the following initial drafts:

* Fun challenge solution for 2025/ayu
* Fun challenge 2 solution for 2025/dogon
* Fun challenge 3 solution for 2025/dogon
* Fun challenge solution for 2025/ncw2

Ran `make quick_www` to process the above.

TODO: Edit and improve `2025/challenge.md` is/as needed.

Author: lcn2