Move stuff around + add lean and idris experiments

purescript/existentials-blog/src/Exists.purs

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+module Exists where
+
+
+import Prelude
+
+import Data.Exists (Exists, mkExists)
+
+-- type Exists f = forall result. (forall a. f a (a -> result)) -> result
+
+type Forall :: forall k. (k -> Type) -> Type -> Type
+type Forall f r = forall a. f a -> r
+
+{- type Showable a f = Show a => f
+type EConstructor f = forall a. f a (a -> Exists f)
+
+mkShowable :: EConstructor Showable
+mkShowable a f = f a  -}

purescript/existentials-blog/src/Main.purs

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+module Main where
+
+import Prelude
+
+import Effect (Effect)
+import Effect.Console (log)
+
+main :: Effect Unit
+main = do
+  log "🍝"