saldl.1: Mention that --custom-headers can be passed multiple times
saldl.1: Mention that --custom-headers can be passed multiple times

Signed-off-by: Mohammad Alsaleh <6c225a8dcf0f3ea8ab31a8a88dea0c937d544fc7@gmail.com>

saldl/saldl,saldl/saldl,saldl/saldl