RFR: 8340815: Add SECURITY.md file [v3]

[Julian Waters]

On Wed, 25 Sep 2024 06:28:18 GMT, George Adams <gdams at openjdk.org> wrote:

>> Currently the [security tab](https://github.com/openjdk/jdk/security) on the GitHub repos is empty with no clear information or links on where to report security vulnerabilities.
>> 
>> <img width="1278" alt="Screenshot 2024-09-24 at 14 28 37" src="https://github.com/user-attachments/assets/4fd68f9f-46d8-4c06-ad71-52747c8f5cf2">
>> 
>> I've added a simple SECURITY.md file which includes the link to the official policy on the website.
>
> George Adams has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Feedback from Mark

Marked as reviewed by jwaters (Committer).

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PR Review: https://git.openjdk.org/jdk/pull/21155#pullrequestreview-2328309381