document technique for updating an individual key about seamless-immutable

[robjens]

AFAIK (just got to learn this library), the only supported types are Object and Array.

Immutable List isn't to be found. Also the amount of available methods is seriously trimmed down.

However, that having said, there is a way to accomplish what you desire, I've used ES5 function notation here...

Immutable([1 2 3]).flatMap(function(x) { return x == 1 ? x + 1 : x; });

Should do the trick.

[rtfeldman]

I'd do what @robjens suggested! 👍

Happy to accept a PR adding this technique to the README, but closing this issue in the meantime.