add entry for 3.0 to init script

[emilypi]

The prompt for 3.0 requires some feedback. Otherwise, this addresses #6239

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[fgaz]

There's also the multiple public libraries / public sublibraries / public named libraries feature

[emilypi]

@fgaz I discussed the feature list with @hvr, and we came to what was written as the conclusion. There are too many things to list in the prompt to make it reasonably informative between 2.4 -> 3.0, so some features are not going to be mentioned.

[m-renaud]

Hey @emilypi, thanks for the PR, and sorry for the slow turn around on this. It appears this was done as part of a general cabal init cleanup in 2fa8302 so I'm going to close this out.

[emilypi]

No worries @m-renaud thanks