Add prompt ability

[randoogle]

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I find that I often have to convert a configuration file from one environment to several other environments. Rather than doing 5 separate find/replaces for each of the 6 environments, I'd love to make a boop script that can do it for me. Unfortunately, there's no way to prompt a user for input, since I would need to ask which environment to convert to.

It would be cool if you could implement the javascript prompt() method somehow in boop.

[muescha]

i miss also the prompt command