add cookie-parser as a dependency and add .cookie to Middleware module

package.json

@@ -5,6 +5,7 @@
   "main": "index.js",
   "dependencies": {
     "body-parser": "^1.18.3",
+    "cookie-parser": "^1.4.5",
     "express": "^4.16.3"
   },
   "devDependencies": {

src/Express.re

@@ -442,6 +442,7 @@ module Middleware = {
     "type": string,
     "limit": Js.Nullable.t(int),
   };
+  type cookieOptions = {. "decode": option(string => Js.Json.t)};
   [@bs.module "express"] [@bs.val] external json_ : jsonOptions => t = "json";
   [@bs.module "express"] [@bs.val]
   external urlencoded_ : urlEncodedOptions => t = "urlencoded";
@@ -488,6 +489,10 @@ module Middleware = {
       "limit": ByteLimit.toBytes(limit),
       "inflate": inflate,
     });
+  [@bs.module "cookie-parser"] [@bs.val]
+  external cookie_: (option(string), cookieOptions) => t = "raw";
+  let cookie = (~secret=?, ~decode=?, ()) =>
+    cookie_(secret, {"decode": decode});
   module type S = {
     type f;
     type errorF;

src/Express.rei

@@ -304,6 +304,7 @@ module Middleware: {
       unit
     ) =>
     t;
+  let cookie: (~secret: string=?, ~decode: string => Js.Json.t=?, unit) => t;
   module type S = {
     type f;
     let from: f => t;