Legal precedent is changing, and ADA compliance related lawsuits are becoming more successful, and the courts are seeing more of them as a result. Title III of the Americans with Disabilities Act pertains to private sector businesses. Lately, those protections are more frequently expanding into digital territory as web and mobile applications become more necessary in our day-to-day lives.
Aloha Tatiana! I wish your questions had straightforward easy answers – and if you are government funded it kind of is. (See here: https://www.ada.gov/websites2_prnt.pdf) if you are not government funded, this is something that is currently being debated in the legal system. That being said, the WCAG 2.0 guidelines are a good set of guidelines to help protect yourself if you feel you should. (You can see more on WCAG here: https://www.yokoco.com/find-out-how-to-make-your-website-compliant/)