Support for Itsy Package Management System (ipkg)

[kzantow]

What would you like to be added:
Support for the Itsy Package Management System (aka 'ipkg')

This should probably include an itsy or similar namespace in the PURL, based on the deb type docs.

Why is this needed:
To catalog more package ecosystems.

Additional context:
First noted in #2692:

...filesystems built using the Itsy Package Management System (aka 'ipkg') that appear to have the exact same status file format used by Debian (dpkg) and OpenWRT (opkg). I believe that simply adding a glob of **/lib/ipkg/status would handle these filesystems as well.