Add support for COMP-3 numbers without the sign nibble

We are using cobrix to convert the mainframe EBCDIC file. Below are the problematic data fields:

XXX-TRANSACTION-AMOUNT PIC S9(15) V99 COMP-3

We are not able to convert the fields correctly. I suspect due to sign field we are running into issues and coming as NULL.
Rest all fields are coming correctly.

cobolDataframe = spark.read.format("za.co.absa.cobrix.spark.cobol.source") \
.option("copybook", "dbfs:/FileStore/Optis Test/copybook.txt") \
.option("record_format", "D") \
.option("is_rdw_big_endian", "true")\
.option("rdw_adjustment", -4) \
.load("dbfs:/FileStore/Optis Test/inputfile.txt")

thanks for the help

## Background [Optional]
A clear explanation of the reason for raising the question.
This gives us a better understanding of your use cases and how we might accommodate them.

## Question
A clear and concise inquiry