Backport starter-plugin 0.9.0 changes (#46511)

* Changelog and readme.txt edits.

* Update stable tag in readme.txt

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Co-authored-by: Grzegorz Chudzinski-Pawlowski <>

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/20839864490

Upstream-Ref: Automattic/jetpack@c70d5de

Author: grzegorz-cp