Announcement: sunsetting EcologicalNetworks and preparing the replacement

[tpoisot]

Important announcement: in order to build the next steps of this package on a healthier code-base, it has been decided (by me! I can do this!) to sunset this package starting now (June 23, 2023), and to replace it with the feature equivalent package SpeciesInteractionNetworks.

EcologicalNetworks will (i) remain accessible on GitHub (although archived), (ii) remain published on the Julia registry, and (iii) not receive patches/updates. The goal is to make SpeciesInteractionNetworks faster, more flexible, and user-friendlier.