Добавлен оператор объединения с null

Author: aNNiMON

src/main/java/com/annimon/ownlang/parser/Lexer.java

@@ -83,6 +83,7 @@ public static List<Token> tokenize(String input) {
         OPERATORS.put("**", TokenType.STARSTAR);
         OPERATORS.put("^^", TokenType.CARETCARET);
         OPERATORS.put("?:", TokenType.QUESTIONCOLON);
+        OPERATORS.put("??", TokenType.QUESTIONQUESTION);
     }
 
     private static final Map<String, TokenType> KEYWORDS;