Fix /nix/store taking up a lot of storage

Additionally:
- add arcaea wiki search engine
- fix haskell devshell not evaluating
- remove a big dependency from my neovim setup

devshells/haskell.nix

@@ -5,7 +5,7 @@ pkgs.mkShell {
     ghc
     hpack
     stack
-    fourmolu # Formatter
+    haskellPackages.fourmolu # Formatter
     cabal-install
     haskell-language-server
     haskellPackages.implicit-hie # Automatically generate hie.yaml!