feat(repo): initialise repository

flake/package.nix

@@ -0,0 +1,4 @@
+{ haskellPackages }:
+haskellPackages.developPackage {
+  root = ../.;
+}

flake/shell.nix

@@ -0,0 +1,14 @@
+{
+  mkShell,
+  haskellPackages,
+}:
+mkShell {
+  name = "haskell";
+  packages = builtins.attrValues {
+    inherit (haskellPackages)
+      haskell-language-server
+      ormolu
+      ghc
+      ;
+  };
+}

flake/treefmt.nix

@@ -0,0 +1,5 @@
+_: {
+  projectRootFile = ".git/config";
+  programs.nixfmt.enable = true;
+  programs.ormolu.enable = true;
+}