Undeclared peerDependency on prop-types

[TheLarkInn]

Looking at:

react-lottie/src/index.js

Line 2 in 56f7284

import PropTypes from 'prop-types';

prop-types is explicitly used inside of the production code of this package, however it is only declared as a devDependency. This needs to be declared as a peerDependency if users are expected to "bring-their-own" version of prop-types.