`[\n]` should not match `\r\n`

[hamishknight]

Currently [\n] matches \r\n in grapheme semantic mode, however this should not be the case.

[milseman]

This is open for debate as to whether we consider \n to be a literal scalar escape or some kind of newline character class.

[hamishknight]

@milseman AFAIK other engines treat [\n] as equivalent to \n. We could define it differently, though that would also mean we'd also have to ban its use as a range operand e.g [\n-0]

[hamishknight]

Oh hey looks like Lily already fixed this in #525, adding a couple more tests in #570

[hamishknight]

Happy to re-open if we decide we want a custom matching behavior instead