Creating an ‘other’ field

Is there a way to create an ‘other’ option for a multiselect checkbox field?

For example, when a user is signing up there may be a field titled ‘Area of expertise’ which has multiple checkboxes the user can select such as ‘Art’, ‘Art History’ etc. but I also want to have an ‘other’ option so that the user may type in a selection that isn’t listed.