Add note that "world-state isn't saved" to the Save feature to avoid frustration

[quiddity-wp]

We tried creating a Gosper glider gun at https://ncase.me/sim/?s=conway and then saving it to share with others. It seems that the "Save" feature just saves the Rules, and then randomly populates the grid per the World settings.

• If this is intentional, it would be good to add a note to the UI warning people that "the world-state is not saved, just the rules" (or similar), to avoid frustrations.
  • (somewhere around here: https://github.com/ncase/sim/blob/gh-pages/scripts/engine/Editor.js#L104)
• If this is a bug, re-title accordingly!

P.s. Thanks as ever for the great web-tool!