Improve error reporting

[prsabahrami]

I think the error reporting and printing is not very organized at the moment. Maybe we can try creating an error.rs containing different error structs for simple commands or if statements and then implement into_diagnostic() for all of them to add miette support. I'll try to open a PR with an idea of how I think would be good to handle this week. Let me know if you have any good idea in mind on what's good way to handle errors.