Amended the wpcomsh plugin readme file. (#37901)

* Added accurate README information and links.

* Changelog.

* Version changes.

* More clarity and fixing omissions.

* Removed redundant commands.

* Update projects/plugins/wpcomsh/README.md

Co-authored-by: Brad Jorsch <anomiex@users.noreply.github.com>

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Co-authored-by: Brad Jorsch <anomiex@users.noreply.github.com>

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/9552826589

Upstream-Ref: Automattic/jetpack@f6858da