Since so much of our plans now runs through the app, most of us want to stay connected. I will echo other posters. Don't rely on the availability of outlets because you won't often find one and it's not very fun to be tethered to the wall while everyone else is either waiting on you or off having fun. Spend the few dollars on a portable charger. Many inexpensive, dependable brands have been mentioned, and it's all good advice.
That being said, I find the outlets in Cosmic Rays at MK and in the restrooms between Future World and the WS at Epcot to be the most available.