Add disclaimer, and fix links (#5)

*Issue #, if available:*

*Description of changes:*
Adds disclaimer that this project is not endorsed by Rust foundation and
fixes license links.

By submitting this pull request, I confirm that you can use, modify,
copy, and redistribute this contribution, under the terms of your
choice.

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Co-authored-by: Celina G. Val <celinval@amazon.com>