[5pt] Release notes for `2.10.0-beta1`

[xuniq]

Release notes for 2.10.0-beta1 (August 2021 releases)

Source document: https://github.com/tarantool/tarantool/releases/tag/2.10.0-beta1
Deploy: https://develop.tarantool.io/ru/doc/gh-2316-beta-changelog/release/2021-08-releases/
Connected with #2305

Product: Tarantool
Root document: https://www.tarantool.io/en/doc/latest/release/
SME:
Peer reviewer:

Definition of done

• Proofread release notes for 2.10.0-beta1
• Check and add suggestions from this comment to changelog