Add alt text help article

[superplane39]

No description provided.

[cellio]

Looks good! There are a couple tips at https://judaism.meta.stackexchange.com/questions/3426/lets-make-mi-yodeya-more-friendly-to-people-and-machines-that-cant-see-images that might be helpful too, specifically:

• Don't say "image of"; the screenreader will do that already.
• If there's nothing more to say -- the image is decorative or the surrounding text already describes the image (and the image is just there for proof), use empty alt text.
• Prefer actual text (transcriptions) over photos of pages from books, but if the latter is all you can do, provide the salient points in the alt text rather than just saying something like "Design of Everyday Things, page 31".