Warn users if a `Str` literal contains invisible unicode characters

[lukewilliamboswell]

Provide a warning if a Str literal contains invisible unicode characters

See zulip discussion for more context

example module

module []

# this string has invisible unicode in it... let's provide a warning to make this obvious
stringWithInivisbleUnicode = "FOO"

expect stringWithInivisbleUnicode == "FOO" # false

REPL

Using the real to show what the str contains.

» Str.toUtf8 "\u(feff)FOO"

[239, 187, 191, 70, 79, 79] : List U8

[hrishisd]

Hey, I'm interested in working on this.

[skyqrose]

Related (also about invisible unicode characters): https://github.com/roc-lang/roc/issues/6929 https://github.com/roc-lang/roc/issues/6927

[Anton-4]

It's possible that parts of https://github.com/roc-lang/roc/pull/7730 could be used here as well.