Add bbox field to bigbrain sections

[AhmetNSimsek]

Please see FZJ-INM1-BDA/siibra-python#583 for the intended use.

EDT: Need to recalculate after FZJ-INM1-BDA/siibra-python#591

[AhmetNSimsek]

@xgui3783 This PR aims to speed up the spatial queries. Timo has suggested we should also add bounding boxes to maps and spaces. This, however, bloats the maps with many volumes. Any alternative ideas on how to resolve this?

[xgui3783]

LGTM, with two comments:

1/ I am concerned that by adding bounding box, we now have two sources of truth. I would make sense to do a sanity check (at least when the bounding box property is added) to ensure that both sources of truth agrees

2/ when you do json.dump in python, it does not automatically add a new line at EOF. it would be ideal to write a new line after json.dump

[xgui3783]

This, however, bloats the maps with many volumes. Any alternative ideas on how to resolve this?

The downside of using the static typing approach, I suppose.

the alternative is to add fetching of bounding box to warm cache