Add developing section to README

Add jupyter to flake.nix dev shell

Return error when evaluation failed

feat(nix): add darwin support in flake

not enabling it in ihaskell make nix flake check fail for jupyterWith

Print where kernel is installed

improve flake by distinguishing different goals (development vs final executable vs with a jupyter environment)

we used to expose just the ihaskellEnv. Also added devShell and attribute set for 921. I've renamed some of the packages on the same model as haskell-language-server.

IHaskellPrelude imports most of it

Remove imports

to make the buildlogs clearer

to fix build issues