chore(docs): Include SpiceDB in the list of projects using Ristretto (#285)

[joshua-goldstein]

Problem

Readme was updated in master branch. We cherry pick this commit into main.

Solution

Cherry pick from PR 285.

Original Commit Info

Include SpiceDB in the list of projects using Ristretto.

Signed-off-by: Jimmy Zelinskie jimmy@zelinskie.com
(cherry picked from commit 55e7615)

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[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}