Add security policy link to README.md

[thepetk]

Description of Changes

Simply adds a link to devfile org security policy after the implementation of devfile/api#1627

Related Issue(s)

Fixes devfile/api#1627

Acceptance Criteria

Tests

• Test Coverage
  • Are your changes sufficiently tested, and are any applicable test cases added or updated to cover your changes?
• Gosec scans
  • Fix all MEDIUM and higher findings and/or annotate a finding per gosec instructions: https://github.com/securego/gosec#annotating-code to address why a finding is not a security issue

Documentation

• Does the registry operator documentation need to be updated with your changes?

Tests Performed

Explain what tests you personally ran to ensure the changes are functioning as expected.

How To Test

Instructions for the reviewer on how to test your changes.

Running Unit Tests

Running Integration Tests

Notes To Reviewer

Any notes you would like to include for the reviewer.

[michael-valdron]

/lgtm

[openshift-ci]

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