Added middleware to automatically use utf-8 if no content-type is in …

…the response

include/crow/middlewares/utf-8.h

@@ -0,0 +1,27 @@
+#pragma once
+#include "crow/http_request.h"
+#include "crow/http_response.h"
+
+namespace crow
+{
+
+    struct UTF8
+    {
+        struct context
+        {
+        };
+
+        void before_handle(request& /*req*/, response& /*res*/, context& /*ctx*/)
+        {
+        }
+
+        void after_handle(request& /*req*/, response& res, context& ctx)
+        {
+            if (get_header_value(res.headers, "Content-Type").empty())
+            {
+                res.set_header("Content-Type", "text/plain; charset=utf-8");
+            }
+        }
+    };
+
+}