Add custom alt text to contributor photos

[MichSpieler]

Feature Description

As a user I would like to be able to add alt text to contributor photos.

Feature Use Case

This feature was requested for a book that is a collection of comics. The author pictures are drawings and it is important to the user to be able to describe the authors and the art style in the alt text.

[SteelWagstaff]

+1. This is important for accessibility purposes. Still relevant. Could be addressed along with pressbooks/pressbooks#3729?

[cmurtagh]

Hey team! Please add your planning poker estimate with Zenhub @arzola @fdalcin @ho-man-chan @MichelleWeremczuk @richard015ar @tw77