Support escape from standard
https://www.haskell.org/onlinereport/haskell2010/haskellch2.html
2.6 Character and String Literals
char → ' (graphic⟨' | \⟩ | space | escape⟨&⟩) ' string → " {graphic⟨" | \⟩ | space | escape | gap} " escape → \ ( charesc | ascii | decimal | o octal | x hexadecimal ) charesc → a | b | f | n | r | t | v | \ | " | ' | & ascii → ^cntrl | NUL | SOH | STX | ETX | EOT | ENQ | ACK | BEL | BS | HT | LF | VT | FF | CR | SO | SI | DLE | DC1 | DC2 | DC3 | DC4 | NAK | SYN | ETB | CAN | EM | SUB | ESC | FS | GS | RS | US | SP | DEL cntrl → ascLarge | @ | [ | \ | ] | ^ | _ gap → \ whitechar {whitechar} \
Hightlight escape like in java