Add examples for seed development studies

As proposed by @EmyrClement we could add some example e.g. a notebook that would show users how to prototype complex seeds by doing threshold scans in multiple dimensions.

An example would be the QuadJet+HT+Btag see, for which a 2D plot was made in the DP Note:
https://twiki.cern.ch/twiki/pub/CMSPublic/Level1TriggerPhase2BTaggingNN/simple_HT_bSum_HH4b_SigEff.png

I reproduced this kind of plot in this notebook, so we might want to adapt it to nano and add to the repo as an example:
https://gist.github.com/artlbv/4c9dec6b40acf8f67c34edd5674cf8e8