Image description generation

[liz-desartiges]

Is your feature request related to a problem? Please describe.
Having to write manually image description is a bit cubersome, on apple device the IceCubes provide image description generation, I supposed based on openai tech how it's described on the project readme.

I would like a similar feature within megalodon

Describe the solution you'd like
A button when editing alt text to generate a description of the current image

Additional context
see IceCubes repo