Designing games to be playable by everyone is important to consider early in the design process. Review guidelines and challenges that people face to figure out what elements of your game will benefit from accessibility features. Here's a few resources to get your started.
Game Accessibility Guidelines
This site groups guidelines into Basic, Intermediate and Advanced categories, so that one can choose a level of investment in accessibility features. The guidelines are a collaborative effort from a group of studios, specialists, and academics.
Can I Play That
This site is a treasure trove of reviews and news of real-world games and their adoption of accessibility features. They also offer workshops and already work with some high profile AAA studios.
Free Unity Courses
The training site, raywenderlich.com, offers 2 free training courses on how to practically implement accessibility features in Unity games.