maintainers.inc: add python3-spdx-tools and dependencies

maintainers.inc: add python3-spdx-tools and dependencies

Add maintainers for new packages and also some copied from meta-python:
python3-beartype, python3-booleanpy, python3-click, python3-isodate,
python3-license-expression, python3-rdflib, python3-spdx-tools,
python3-uritools, python3-xmltodict

Signed-off-by: Marta Rybczynska <mrybczynska@syslinbit.com>
Signed-off-by: Samantha Jalabert <samantha.jalabert@syslinbit.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>