workflows: rebase.yml: don't pass empty additional-params as arg

When a caller leaves additional-params unset, the quoted
"$ADDITIONAL_PARAMS" was forwarded as an empty fifth positional
argument. rebase.sh requires exactly four, so it printed usage and
exited 1. Collect the value into an array so an empty string adds no
argument while multiple flags still split correctly.

Signed-off-by: Michał Iwanicki <michal.iwanicki@3mdeb.com>

.github: workflows: trigger-woodpecker-pipeline.yml: add

Signed-off-by: Danil Klimuk <daniil.klimuk@3mdeb.com>