Implement optional chaining (#5164)

The work is based on PR #4843, only fixed some conflicts and cppcheck errors.

Co-authored-by: Robert Fancsik robert.fancsik@h-lab.eu
JerryScript-DCO-1.0-Signed-off-by: Gergo Csizi gergocs@inf.u-szeged.hu

jerry-core/parser/js/js-lexer.h

@@ -154,6 +154,7 @@ typedef enum
   LEXER_RIGHT_PAREN, /**< ")" */
   LEXER_RIGHT_SQUARE, /**< "]" */
   LEXER_DOT, /**< "." */
+  LEXER_QUESTION_MARK_DOT, /**< "?." */
   LEXER_SEMICOLON, /**< ";" */
   LEXER_COLON, /**< ":" */
   LEXER_COMMA, /**< "," */