examples/storage/01-user: Set up for web builds.

examples/categories.txt

@@ -7,6 +7,7 @@
 renderer
 input
 audio
+storage
 camera
 asyncio
 pen

examples/storage/01-user/README.txt

@@ -0,0 +1,5 @@
+This example code creates an SDL window and renderer, and waits for the user
+to click on the window. By default, the window color is blue; When storage
+succeeds, the window turns green, if it fails the window turns red and the
+error message is logged. Left clicking will save a game, all other clicks
+will load a game.