Add NOTICE.txt

NOTICE.txt

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+                            The Hummingbird Project
+                            ====================
+
+Please visit the Hummingbird web site for more information:
+
+  * https://hummingbird.codes
+
+Copyright 2024 The Hummingbird Project
+
+The Hummingbird 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.
+
+-------------------------------------------------------------------------------
+
+This product contains code from swift-foundation.
+
+  * LICENSE (MIT):
+    * https://github.com/swiftlang/swift-foundation/blob/main/LICENSE.md
+  * HOMEPAGE:
+    * https://github.com/swiftlang/swift-foundation/
+