maintainers: Add GNSS Subsystem entry

Listed GNSS drivers maintainer as the maintainer for this area to
retain autonomy on decisions related to GNSS, and listed myself as
collaborator to follow-on with features, bugs and other requests
regarding the modules introduced RTK-related.

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

Author: ubieda

MAINTAINERS.yml

@@ -2468,6 +2468,13 @@ Formatted Output:
     - utilities.prf
     - libraries.cbprintf
 
+GNSS Subsystem:
+  status: maintained
+  maintainers:
+    - bjarki-andreasen
+  collaborators:
+    - ubieda
+
 Google Platforms:
   status: maintained
   maintainers: