Save current map state in IndexedDB or local storage

[Dan Fabulich]

If you refresh or navigate away, the current map is lost. (There's a beforeunload handler to protect you, which helps somewhat.)

It would be better if the current map state were stored in IndexedDB or local storage. Then you could refresh the page or navigate away and come back later, and the map would still be there waiting for you.

[Alexander van Oostenrijk]

I've removed the beforeunload event. Instead, on unload, the current map gets saved to localStorage. When Trizbort.io opens, it attempts to load a map from localStorage, if there is one. This is overruled when Trizbort.io is loaded a map from a URL, though (which would effectively overwrite your localStorage map unless you kill the browser).