add attribution

Author: dignifiedquire

LICENSE-MIT

@@ -1,6 +1,7 @@
 The MIT License (MIT)
 
 Copyright (c) 2019 Yoshua Wuyts
+Copyright (c) 2017 http-rs authors (type_map)
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

src/type_map.rs

@@ -1,3 +1,7 @@
+// Implementation is based on
+// - https://github.com/hyperium/http/blob/master/src/extensions.rs
+// - https://github.com/kardeiz/type-map/blob/master/src/lib.rs
+
 use std::any::{Any, TypeId};
 use std::collections::HashMap;
 use std::fmt;