ghc: Add a configuration for GHC

Copied from Emily Pillmore's configuration.
https://gist.github.com/emilypi/cafa2a0dac8c879b2a2916dab71a3f3f

ghc/.ghc/ghci.conf

@@ -0,0 +1,36 @@
+-- -------------------------------------------------------------------- --
+-- Default Extensions
+
+:set -XRankNTypes
+:set -XGADTs
+:set -XTypeFamilies
+:set -XTypeApplications
+:set -XBangPatterns
+:set -XMagicHash
+:set -XMultiParamTypeClasses
+:set -XPatternSynonyms
+:set -XDataKinds
+:set -XConstraintKinds
+:set -XOverloadedStrings
+:set -XNumericUnderscores
+:set -XFlexibleContexts
+:set -XScopedTypeVariables
+:set -interactive-print=Text.Pretty.Simple.pPrint
+
+-- -------------------------------------------------------------------- --
+-- Warning flags for safe build
+-- https://lexi-lambda.github.io/blog/2018/02/10/an-opinionated-guide-to-haskell-in-2018/
+
+:set -Wall
+:set -Wcompat
+:set -Wincomplete-record-updates
+:set -Wincomplete-uni-patterns
+:set -Wredundant-constraints
+
+-- -------------------------------------------------------------------- --
+-- Util cmds
+
+:def hlint const . return $ ":! hlint \"src\""
+:def hoogle \s -> return $ ":! hoogle --color --count=15 " ++ show s
+:def rg \s -> return $ ":! rg " ++ s
+:def fzf const . pure $ ":! cat $HOME/.ghc/ghci_history | fzf --height 25"