add noitice file (#3321)

motivation: follow best practices for apache licensed projects

changes: add notice file with references to any derived code

Author: tomerd

NOTICE.txt

@@ -0,0 +1,46 @@
+
+                            The SwiftPM Project
+                            ====================
+
+Please visit the SwiftPM web site for more information:
+
+  * https://github.com/apple/swift-package-manager
+
+Copyright (c) 2014 - 2021 Apple Inc. and the Swift project authors
+
+The Swift Project licenses this file to you under the Apache License,
+version 2.0 (the "License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at:
+
+  https://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+License for the specific language governing permissions and limitations
+under the License.
+
+Also, please refer to each LICENSE.txt file, which is located in
+the 'license' directory of the distribution file, for the license terms of the
+components that this product depends on.
+
+-------------------------------------------------------------------------------
+
+
+This dependency resolver is influenced by Dart project (pub tool).
+
+  * LICENSE (BSD 3-Clause "New" or "Revised" License):
+    * https://github.com/dart-lang/pub/blob/master/LICENSE
+  * HOMEPAGE:
+    * https://dart.dev
+    * https://github.com/dart-lang/pub
+
+---
+
+This product contains a derivation of Vapor's JWTKit library, specifically `JWTParser.swift`, `JWTSerializer.swift` and `Base64URL.swift`.
+
+  * LICENSE (MIT License):
+    * https://www.apache.org/licenses/LICENSE-2.0
+  * HOMEPAGE:
+    * https://vapor.codes
+    * https://github.com/vapor/jwt-kit