feat: split reca models in Ext

[MartinuzziFrancesco]

Checklist

• Appropriate tests were added
• Any code changes were done in a way that does not break public API
• All documentation related to code changes were updated
• The new code follows the
  contributor guidelines, in particular the SciML Style Guide and
  COLPRAC.
• Any new documentation only uses public API

Additional context

Closes #197

[MartinuzziFrancesco]

pinging @thazhemadam and @ChrisRackauckas to see if workflows and docs are going in the right direction.

The idea here is to split some ReservoirComputing models into their own packages with standalone installation and documentation. The first of these packages is ReservoirCellularAutomata, since these architectures are already in ReservoirComputing. These packages should live in lib, and have their own tests/docs/version. The idea is to expand these in the future and have ReservoirComputingBase, LiquidStateMachines etc...

Essentially, I am going for something similar to GraphNeuralNetworks.jl, with a multi lib repo, but with a structure that resembles Lux.jl's, that keeps the additional libraries under lib

[MartinuzziFrancesco]

gentle ping for this

[ChrisRackauckas]

It's just 1 dep, right? Any reason this shouldn't just be an extension?

[MartinuzziFrancesco]

It's just one dependency, but the reasoning behind splitting in a new package is that ReservoirCellularAutomata exports new models and methods, not just simple dispatches

[MartinuzziFrancesco]

adding this to ext

[MartinuzziFrancesco]

closing this, cleaner version on #299