Yes raw chicken and other raw meats can be put into a slow cooker to cook along with the other food or to just cook the raw chicken by itself.
I always just put raw chicken or raw meats into my slow cooker to allow the chicken or other meats to cook as there is no need to cook the chicken or other meat beforehand.
The slow cooker will slowly cook the chicken and other meats over the time you leave the slow cooker on.
You can cook the chicken before putting it into the slow cooker to make the chicken take less time to cook and be ready.
However leaving the chicken in the slow cooker over 8 hours or overnight will fully cook the chicken to where it's safe to eat.