feat: support alt text via \Description command in ACM template

[jooyoungseo]

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Thanks for the great project! As a screen reader user myself reading a lot of ACM articles, I was wondering if you could support alt text inserted via \Description command. Currently, only figure caption is inserted into the alt text. However, when possible, \Description needs to be added as an alt text as it provides further description.

LaTeX users can use the command \Description[]{} inside every figure, teaserfigure, marginfigure, or table environment to provide a description of the image(s) used in the figure.

Retrieved from https://authors.acm.org/journals/how-to-write-alt-text-and-why#h-how-to-write-alt-text-in-latex

[dginev]

Thank you for the request @jooyoungseo !

This has been requested before, so this issue is technically a duplicate for #2271 . I will leave both open for now - thank you for reaching out to us.