Toward LLK/scratch-www#2296

This allows us to take you to any destination when clicking the logo, or to do something else, or nothing at all.

If no handler is provided, the logo will not be clickable.

That is, as the default value for the input, not the placeholder.

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

Liked @paulkaplan’s suggestion that the property get renamed `showBranding` as we use ‘embedded’ in multiple ways that would get confusing.

The embedded project view is ‘playerOnly’, ‘fullscreen’ and ‘showBranding’.

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

Fixes 2 related issues:
1. The stage shrinking to 85% based on responsive stylings, which shouldn't happen when embedded in player only
2. When you click "small stage mode" in the editor then switch back to the project page view, it shouldn't show with small stage mode.

Instead of setting 100% width on the message, causing inappropriate wrapping of the button text. Removed the nbsp in the Try Again text

I do not like how the alert component is hyper specialized for two distinct use cases. It would be much better to refactor the alerts so that the alerter can just fill the alert with whatever they want. But I do not feel comfortable making that refactor because I know ben and evelyn have gone back and forth about these alerts.

We have alerts for this now.
Resolves #3893

Fixes issue #3269