Add BucketMate to the Developers list

[davidtranjs]

0. I have read the Contribution Guidelines
1. Project URL: https://bucketmate.app
2. Why should this project be added: It helps developers manage multiple S3-compatible storage better with great UI/UX and native macOS performance. No more confuse web interface and complex CLI commands
3. End all descriptions with a full stop/period
4. Entry is ordered alphabetically
5. Appropriate icon(s) added if applicable (OSS, freeware)