Add a basic NOTICE.md to clarify the used licensing term

NOTICE.md

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+## Copyright
+
+All content is the property of the respective authors or their employers. For more information regarding authorship of content, please consult the listed source code repository logs.
+
+## License
+
+This project is licensed under the Apache License, Version 2.0 ([LICENSE](LICENSE) or <http://www.apache.org/licenses/LICENSE-2.0>). Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be licensed as above, without any additional terms or conditions.