maintainers: Add GNSS Subsystem entries

To be covered by existing Drivers: GNSS, as per requested during the
review process. Added myself as a collaborator to follow-up with
RTK-related changes.

Signed-off-by: Luis Ubieda <luisf@croxel.com>

Author: ubieda

MAINTAINERS.yml

@@ -1569,21 +1569,26 @@ Release Notes:
   collaborators:
     - tomi-font
     - fabiobaltieri
+    - ubieda
   files:
     - doc/hardware/peripherals/gnss.rst
     - drivers/gnss/
     - include/zephyr/data/navigation.h
     - include/zephyr/drivers/gnss.h
     - include/zephyr/drivers/gnss/
+    - include/zephyr/gnss/
     - dts/bindings/gnss/
     - include/zephyr/dt-bindings/gnss/
     - tests/drivers/build_all/gnss/
     - tests/drivers/gnss/
+    - tests/subsys/gnss/
     - samples/drivers/gnss/
+    - subsys/gnss/
   labels:
     - "area: GNSS"
   tests:
     - drivers.gnss
+    - gnss
 
 "Drivers: Haptics":
   status: maintained