You will hear many different opinions on tipping housekeeping. Some do not tip at all. Some tip very little because they only come every four days.
Some tip based on accommodation size...ie, more for a 1BR than for a studio.
We always leave a tip, but it does vary based on how many times they cleaned for us, and whether they did anything "above and beyond" for us.
There is no set rule...in fact, I don't even think that Disney lists them as a tipping position.