Proposal? foldAlt :: (Foldable t, Alternative f) => t a -> f a

[Fumiaki Kinoshita]

We found this quite useful, but we are not 100% about the name and
documentation.

-- | Try—in the 'Alternative' sense—to return all the values in a 'Foldable'
-- container.
--
-- @
-- foldAlt ≡ 'listToMaybe' :: [a] -> 'Maybe' a
-- foldAlt ≡ 'maybeToList' :: 'Maybe' a -> [a]
-- foldAlt ≡ 'MaybeT' . 'return' :: ('Monad' m) => 'Maybe' a -> 'MaybeT' m a
-- foldAlt ≡ 'Pipes.ListT' . 'Pipes.each' :: ('Monad' m) => [a] ->
'Pipes.ListT' m a
-- foldAlt ≡ id :: 'Maybe' a -> 'Maybe' a
-- @
foldAlt :: (Foldable t, Alternative f) => t a -> f a
foldAlt = getAlt . foldMap (Alt . pure)
{-# INLINE foldAlt #-}

I propose adding this to either `Data.Foldable` or `Control.Applicative`.
Any thoughts?
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