Create SECURITY.md

[harryvik990]

ATTENTION: ERC-RELATED PULL REQUESTS NOW OCCUR IN ETHEREUM/ERCS

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When opening a pull request to submit a new EIP, please use the suggested template: https://github.com/ethereum/EIPs/blob/master/eip-template.md

We have a GitHub bot that automatically merges some PRs. It will merge yours immediately if certain criteria are met:

• The PR edits only existing draft PRs.
• The build passes.
• Your GitHub username or email address is listed in the 'author' header of all affected PRs, inside .
• If matching on email address, the email address is the one publicly listed on your GitHub profile.

[eth-bot]

File SECURITY.md

Requires 2 more reviewers from @g11tech, @lightclient, @SamWilsn, @xinbenlv