Ignoring images based on height/width ratio

[HadrienGardeur]

We know that most images in EPUB files are probably decorative but missing the proper information to identify them as such (blank value for alt or using presentation/none in role).

Very long images (long-ish width, small height) for example are very likely to be separators. This was one of our proposals for detecting decorative images presented at DPS24 with @gautierchomel.

With the addition of the --inspect-images flag, we can now calculate the height and width of all images in an EPUB file.

Should we ignore these images automatically or when using a specific flag available on the manifest command? If so, which value(s) should we use in terms of ratio?

(This relates to #18)