[ENH] Self-organising map (SOM) clusterer

[chrisholder]

Describe the feature or idea you want to propose

SOM has been used with DTW in the literature and is easily extendable to all the elastic distances we have in aeon. A link to the first paper I could find that used it was: https://arxiv.org/abs/2004.08176.

Describe your proposed solution

I propose with implement an "ElasticSOM" clusterer.

Describe alternatives you've considered, if relevant

No response

Additional context

No response