Version bump `0.8.5` → `0.8.6`.
### Changed
- Package registry metadata for better discoverability (#259):
- R (R-universe): R-universe URL + `X-schema.org-keywords` in `DESCRIPTION`, package logo at `bindings/r/man/figures/logo.png`.
- Python (PyPI): `Documentation` project URL.
- C# (NuGet): package icon via `PackageIcon`.
Ships the metadata so the next PyPI/NuGet publish carries the new fields (R-universe rebuilds from main independently). Bump touches the manual release touchpoints only; docs/webpage version strings are left to `sync-about.yml` on the tag.
kingchenc
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