[8.14] Add license (backport #1121)

[mergify]

Relates to elastic/docs#2396

This PR adds the https://creativecommons.org/licenses/by-nc-nd/4.0/ license.
It also updates the readme per https://github.com/santisoler/cc-licenses?tab=readme-ov-file#cc-attribution-noncommercial-noderivs-40-international

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This is an automatic backport of pull request #1121 done by Mergify.

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[mergify]

This pull request has not been merged yet. Could you please review and merge it @lcawl? 🙏

[mergify]

This pull request has not been merged yet. Could you please review and merge it @lcawl? 🙏

[mergify]

This pull request has not been merged yet. Could you please review and merge it @lcawl? 🙏