Use `just` tool to run examples

[phil-opp]

This PR tries to replace our custom run.rs files with the just tool. The goal is to make the commands more obvious to users.

[Michael-J-Ward]

I think this would be much cleaner and more approachable for rust and non-rust devs alike.

[haixuanTao]

This would be awesome but just encountered this issue: https://github.com/casey/just/pull/1229/files , which is about how just might not be super practical with virtual env. The fix proposed cold potentially work but we would need to bake it into the dataflow which might not be super ideal. I'm kind of looking at the ways other people fixed it but might be a bit hacky

[haixuanTao]

I'm wondering if we can just use a nu script that will fix the conda shell environment. https://www.nushell.sh/book/scripts.html

[phil-opp]

Closing on favor of https://github.com/dora-rs/dora/pull/495