Ignoring very small images

[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 small images are likely to be decorative since they can hardly convey relevant information. 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, what's the minimum width or height (in pixels) that we'd like to use? What about gaiji (Japanese kanji using images since they might be missing in font files)?

(This relates to #18)