Think not all valid unicode escapes in strings are supported

[eugenesvk]

10FFFF is a valid codepoint, but raises an error

Error:
  × Found invalid node name
   ╭────
 1 │ a "\u{10FFFF}"
   ·              ┬
   ·              ╰── not node name
   ╰────
  help: This can be any string type, including a quoted, raw, or multiline string, as well as a plain identifier string.