Add config for Next.js

[samrobbins85]

By default, Next.js builds to the folder out when the command next export is used. I can't think of an alternate use for the out directory beyond builds, so I think it would be useful if this is one of the defaults.

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[samrobbins85]

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[patrickhulce]

thanks @samrobbins85 great addition!

I agree out seems pretty safe, so I'm OK shipping this without a breaking change 👍