This should have happened a long time ago, but the Fastly config prevented it

randomize sprite positions when added from image file or from library (through 'choose from library' and 'surprise')

Resolves #3950.

Unfortunately the design of scratch-storage doesn't make having multiple distinct POST urls easy at the moment. So for the time being, just make this request ourselves.

We are emitting targets update because the event is disabled in player mode, but gets re-enabled and re-emitted when switching back. The API on that function was changed to allow events to be marked "not project changes"

Adding relevant EV3/WeDo2 tutorial vid links, fixing up some json, removing some prop validation, etc.

use blue creating screen for new projects; revised alert text for copy, remix; saving messages don't dismiss alerts