Fiddle: Fiddle overwrite warning with ⌘N

[codebytere]

Right now when you hit the hotkey for New Fiddle (⌘N), it automatically overwrites the existing one that was open. From a user perspective, it is probably cleaner to trigger a similar interstitial confirmation dialog that gets opened when users load in a new fiddle from gist:

cc @felixrieseberg @erickzhao what do y'all think? happy to take this if you agree!

[felixrieseberg]

Makes perfect sense to me, good idea!

[codebytere]

Excited to report that i got myself into a weird state in local dev and you did in fact account for this 🤦‍♀ I don't think there's any new code to write here so i'm just gonna close this out lol