modalai/voxl2: add voxl2-import-core.sh utility script

[paralin]

Adds a script which can be used to import the vendor image:

# Copy the modalai files to the device.
# Replace "root@voxl2" with your voxl2 ip address.
rsync --progress voxl2_platform_1.3.1-0.8.tar.gz root@voxl2:/mnt/persist/voxl2_platform.tar.gz

# Run the importer script to import the image.
ssh root@voxl2
voxl2-import-core.sh /mnt/persist/voxl2_platform.tar.gz

[paralin]

Confirmed working on a test voxl2.