Backlog for "Features" section

## About
Coming from GH-53, there are a few backlog items, and there will be more.

## Details
- [ ] Features: Improve feature pages which are a bit thin, yet, bearing admonitions like **🛠️ This page is currently under construction**.
- Origin: https://github.com/crate/cratedb-guide/pull/53#pullrequestreview-1933287728
- [ ] Feature / Search: Improve layout
- Origin: https://github.com/crate/cratedb-guide/pull/53#discussion_r1529344885 by @surister
- [ ] Feature / Vector: Add example using euclidean distance function
- Origin: https://github.com/crate/cratedb-guide/pull/53#discussion_r1685430878 by @amotl
- [ ] Feature / Geo: What about querying with "donut" shapes?
- Origin: https://github.com/crate/cratedb-guide/pull/53#pullrequestreview-2160610407 by @seut
- [x] Feature / Search: Hybrid Search
- Origin: https://github.com/crate/cratedb-guide/pull/53#pullrequestreview-2191183546
- Worklog: Add article https://cratedb.com/blog/hybrid-search-in-cratedb by @surister
- Done: Fixed with https://github.com/crate/cratedb-guide/pull/106
- [x] Feature / Index: Hybrid Index
- Origin: https://cratedb.com/docs/guide/feature/index/
- Worklog: Use singular "Hybrid Index" instead of the plural form by @geragray
- Done: Fixed with c4fba3a711.