Feature Request: Add SubFigures to Mpf_Figure

Nessuno ha ancora preso questa issue.

Presently the Mpf_Figure class does not support mpl subfigure plots. Subfigures allow encapsulation of a group of subcharts into one figure that can then be embedded easily in the overall figure

Adding the following function to Mpf_Figure class will add in subfigures
``` Python
def add_subfigure(self,*args,**kwargs):

if 'style' in kwargs or not hasattr(self,'mpfstyle'):
style = _check_for_and_apply_style(kwargs)
else:
style = _check_for_and_apply_style(dict(style=self.mpfstyle))

sf = mplfigure.Figure.add_subfigure(self, *args, **kwargs)
sf.mpfstyle = style
self.subfigs += [sf]
return sf
```

Current Alternative solution / workaround is to sub-class Mpf_Figure and add this in. It would be preferable not to have to do this as SubFigure are part of the mpl and should be supported in mpf

Individua la classe Mpf_Figure e i relativi metodi esistenti per la gestione di subplot o figure; l’issue non indica alcun file né alcun test. Confronta questi punti di ingresso con l’API Figure.add_subfigure di Matplotlib, quindi verifica che le subfigure ereditino lo stile pertinente, siano tracciate dalla figure e possano essere utilizzate senza creare una sottoclasse di Mpf_Figure.

Scritto dal modello di indicizzazione a partire dal testo della issue.