Parse bom in UTF-8 .nu files

[eugenesvk]

Related problem

I was struggling to use import a nushell .nu file, getting weird closure_848 error messages until I realized by trying to copy the content of the file to another one that worked that the only difference is the original had a UTF-8 with BOM encoding

Describe the solution you'd like

The file works as BOM is a valid variant of UTF8 (as much as the whole BOM might be annoying)

Describe alternatives you've considered

Converting files to use a BOM-less variant, but given there is not good error message it's tough to rely on being aware of this tiny thing

Additional context and details

There is this closed #164 issue that seems to be about BOM support, but think it only dealt with utf-16?

[timcharper]

Do you have a sample file that fails? Easy way to reproduce?

[eugenesvk]

sure, this 1-line file with a print command fails with an incomprehensible error message that print isn't print :)

1 │ print "bomye.nu"
· ──┬──
· ╰── Command print not found
╰────
help: Did you mean print?

(change extension back to .nu and source it)

bomye.nu.md

[weirdan]

@timcharper this should demonstrate the problem:

"export def main [] { print Hello }" 
| into binary 
| prepend 0x[ef bb bf] # UTF-8 BOM 
| bytes collect 
| save file.nu

then use file.nu