Suggest how to enable a language extension in the repl

Motivation

When using a feature that requires a language extension in a repl it would be nice for ghci to suggest how to enable that extension. Currently it will show:

ghci> data family GMap k :: * -> *

<interactive>:1:1: error:
    • Illegal family declaration for ‘GMap’
        Enable TypeFamilies to allow indexed type families
    • In the data family declaration for ‘GMap’

Even though I've been using haskell for a while I frequently forget what it is (I probably also just have terrible memory). For instance I just tried this out :set -xTypeFamilies forgetting that x needs to be uppercased.

Proposal

ghci> data family GMap k :: * -> *

<interactive>:1:1: error:
    • Illegal family declaration for ‘GMap’
        Enable TypeFamilies to allow indexed type families
    • In the data family declaration for ‘GMap’
Perhaps try enabling the language extension with:
:set -XTypeFamilies

Or something like that.