Add Sealos One-Click Deployment Button to README

Feature Request: Add Sealos One-Click Deployment

Summary

Please add a Sealos one-click deployment button to the README.md file to allow users to easily deploy Nakama on the Sealos cloud platform.

Proposed Addition

Add the following markdown button to the README deployment section:

[![](https://raw.githubusercontent.com/labring-actions/templates/main/Deploy-on-Sealos.svg)](https://gzg.sealos.run/?openapp=system-template%3FtemplateName%3Dnakama&uid=j-LJCRi64u)