Add FWCore/Reflection in support of cms-sw/cmssw#27287

[fabiocos]

Update of https://github.com/cms-sw/cms-bot/blob/master/categories_map.py to add the new package FWCore/Refelction proposed in cms-sw/cmssw#27287 . The package is assigned to the "core" group.

[cmsbuild]

A new Pull Request was created by @fabiocos (Fabio Cossutti) for branch master.

@cmsbuild, @smuzaffar, @gudrutis, @mrodozov can you please review it and eventually sign? Thanks.
cms-bot commands are listed here

[fabiocos]

I would like to merge cms-sw/cmssw#27287 in next IB (@Dr15Jones FYI), so we need to integrate this update earlier

[smuzaffar]

looks good