Write to SIM in Binary

ok = modem.simwb(fileid, addr, txt)
ok = modem.simwb(fileid, txt)

• fileid is the decimal FileID (e.g. 28539) to write to the SIM.
• addr is the optional offset
• txt is the data to write

Uses AT+CRSM=214,XXX,0,0,X,X to write to the SIM.