DEV: add 8.10-rc1 release notes

[dwdougherty]

These RNs are for Redis 8.10.

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Note

Low Risk
Documentation-only addition with no runtime or security impact; placeholder front-matter version fields may need correction before publish.

Overview
Adds redisos-8.10-release-notes.md under the Redis CE / Stack release-notes docs for Redis Open Source 8.10-RC1 (July 2026).

The page documents RC scope (not for production), supported OS matrix, and change lists versus 8.8: new core and module commands (lists/sets/streams, RediSearch timeout policies and FT.ALIASLIST, JSONPath extensions, TimeSeries TS.NRANGE / TS.READ / label and EXCLUDEEMPTY options), bug fixes across core and modules, performance notes, Modules API events, and redis-cli cluster/latency updates. Front matter uses placeholder min-version-db / min-version-rs values of blah.

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[github-actions]

DOC-6550

[github-actions]

Staging links:
https://redis.io/docs/staging/DOC-6550/operate/oss_and_stack/stack-with-enterprise/release-notes/redisce/redisos-8.10-release-notes/

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