Fix file extension "trsipic1_lazur.JPG" -> "trsipic1_lazur.jpg".

These examples are looking for "trsipic1_lazur.jpg", but the file is called "trsipic1_lazur.JPG":
examples/loader/load events.js
examples/sprites/dynamic crop.js
examples/sprites/horizontal crop.js
examples/sprites/vertical crop.js