docs: add memory guide quick try

[RerankerGuo]

Fixes #2081.

Summary

• Add a small optional quick-try note before the local plugin install steps.
• Keep the local-first setup path as the primary flow.

Validation

• Confirmed the quick-try URL returns HTTP 200.
• Confirmed the README still keeps Quick Start followed by 1. Install as the main setup flow.
• make format could not run locally because poetry is not installed: make: poetry: Command not found.

[shinetata]

Thanks again for the PR, @RerankerGuo, and for keeping the local-first setup as the primary flow.

We have decided not to embed third-party marketing/tracking links (app.clawmama.run with utm_campaign=skill_outreach_...) in the open-source README, so we are closing this PR along with the originating request in #2081. This is purely about the nature of the link, not the quality of your work, which we appreciate.

Your other contributions are very welcome, please keep them coming. Thanks for understanding!