Feature Request: config key supporting list of strings

[rdewaele]

I found myself using multitasks in combination with checkbox-style prompts, which I find very convenient. However, sometimes I want to run multiple multitask based off exactly the same selection, in which case I have to add a helper task (or some other fiddly hack) to copy the selection from the original value to multiple places.

Would a pull request implementing this feature be welcome?

The result would be that the selection is written to multiple places in the grunt config instead of just one.