Add a group for libnxz
Add a group for libnxz

Created a group so `libnxz` will appear in the release notes.

Fix #2887

Signed-off-by: Erwan Prioul <9949cc68615082c237e6af925cacbd2ea7f2e953@linux.ibm.com>

advancetoolchain/advance-toolchain,advancetoolchain/advance-toolchain,advancetoolchain/advance-toolchain,advancetoolchain/advance-toolchain,advancetoolchain/advance-toolchain,advancetoolchain/advance-toolchain