Explore the idea of using Bun as the package manager

[Ahmed Elsakaan]

We are currently using pnpm as our package manager, but Bun seems like the fastest solution available right now and as a believer of the Bun project, it would be cool to start using it just as our package manager.

Checks:

• bun install works.
• bun run build builds the project successfully.
• bun typecheck produces no type-errors.
• Update GitHub CI workflow to use bun instead of volta.
• Update our contributing guide to reflect this change.

[Dhechid Phumpaka]

Will be doing the first four task.