Add support for ocamlformat (#32)

Author: huwaireb

README.md

@@ -77,6 +77,7 @@ For an example, see [haskell-template](https://github.com/srid/haskell-template)
 * gofmt
 * gofumpt
 * nixpkgs-fmt
+* ocamlformat
 * ormolu
 * prettier
 * purs-tidy

programs/ocamlformat.nix

@@ -0,0 +1,21 @@
+{
+  lib,
+  pkgs,
+  config,
+  ...
+}: let
+  cfg = config.programs.ocamlformat;
+in {
+  options.programs.ocamlformat = {
+    enable = lib.mkEnableOption "ocamlformat";
+    package = lib.mkPackageOption pkgs "ocamlformat" {};
+  };
+
+  config = lib.mkIf cfg.enable {
+    settings.formatter.ocamlformat = {
+      command = cfg.package;
+      options = ["-i"];
+      includes = ["*.ml" "*.mli"];
+    };
+  };
+}