Add Backpack to project showcase (#567)

Co-authored-by: Billy Chan <[email protected]>

COMMUNITY.md

@@ -9,3 +9,4 @@ If you have built an app using SeaORM and want to showcase it, feel free to open
 - [aeroFans] ([repository(https://github.com/naryand/aerofans)) | Full stack forum-like social media platform in Rust and WebAssembly
 - [mediarepo](https://mediarepo.trivernis.dev) ([repository](https://github.com/Trivernis/mediarepo)) | A tag-based media management application
 - [THUBurrow](https://thuburrow.com) ([repository](https://github.com/BobAnkh/THUBurrow)) | A campus forum built by Next.js and Rocket
+- [Backpack](https://github.com/JSH32/Backpack) | Open source self hosted file sharing platform on crack