Fix require not throwing syntax error

[Someon1e]

Fixes #139

[CompeyDev]

🙏 Thank you for this PR - this pretty simple bug does get quite annoying at times, but I had been procrastinating actually PR'ing a fix for it.

[filiptibell]

Thank you for the PR! Took a look through and it seems good - but I'm wondering if maybe we should go about this a bit differently? With this PR we are checking specifically against syntax errors and returning those early, when we should probably be checking for anything that's not a "file doesn't exist" error and falling through to the next path if we get one of those 🤔

[filiptibell]

Seems like we need to also check for if the error is an "is a directory" error for the first few branches, otherwise requiring dir/init.lua and dir/init.luau as require("dir") below stops working (https://github.com/lune-org/lune/actions/runs/8603776567/job/23634709137?pr=168)

[filiptibell]

Thank you!