Issue-3504-atom-sunset

[charlottejmc]

I've added a warning box (kindly translated by @jenniferisasi) to warn readers that Atom has been shut down, and to recommend using VSCode instead.

Closes #3504

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[charlottejmc]

Thank you @jenniferisasi and @gabrielcalarco for being so quick and helpful!

[jenniferisasi]

Fantastic solution!