Yes, there is a quite simple way to do this!

First, place your expand-script in a good folder, like /usr/local/bin/expand.sh, and make it executable with chmod +x /usr/local/bin/expand.sh

Then, edit /boot/config.txt and add the following furthest down:

[expansion]
init=/usr/local/bin/expand.sh

Reboot, and then observe the expanded filesystem with df -h

Yes, there is a quite simple way to do this!

First, place your expand-script in a good folder, like /usr/local/bin/expand.sh, and make it executable with chmod +x /usr/local/bin/expand.sh

Then, edit /boot/config.txt and add the following furthest down:

[expansion]
init=/usr/local/bin/expand.sh

Reboot, and then observe the expanded filesystem with df -h