Examples for zigbee are using custom license, which is not present
on the SPDX license list. This was discussed on !16205 and a decision
was made that the examples will be put on check-copyright's ignore list.
SPDX has LicenseRef-[idstring] identifier for such cases, so let's try
to use it. In this particular case the LicenseRef-Included is used to
express that the full license text is included in the source file.
Note that the LicenseRef-Included is not part of SPDX. It's just
something I used. No change is needed on the check-copyright side.
Signed-off-by: Frantisek Hrbata <frantisek.hrbata@espressif.com>
