Add SpiceDB project to repositories.toml

[samkim]

Link to issues: https://github.com/authzed/spicedb/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22

ℹ️ Repository information

The repository has:

• [x] At least three issues with the good first issue label.
• [x] At least 10 contributors.
• [x] Detailed setup instructions for the project.
• [x] CONTRIBUTING.md
• [x] Actively maintained.

[vercel[bot]]

@samkim is attempting to deploy a commit to the DeepSource Team on Vercel.

A member of the Team first needs to authorize it.