The requirements are publicly available, happily! Look up “Web Content Accessibility Guidelines.” The most current published version is 2.1, and you need to meet the Level A and AA guidelines to be considered as meeting the minimum accessibility needs. The guidelines can be a little confusing sometimes, but there’s a really active community of web accessibility professionals who are happy to help people get a handle on what you need to do (and no, you do not need sign language interpretation for the written word; being deaf doesn’t prevent you from reading written language).