docs: list 0.9.x as supported

[nightcityblade]

Summary

Add the current 0.9.x release line to the security policy's supported-version table while retaining support for 0.8.x.

Fixes #2216

List of files changed and why

• SECURITY.md — list the current 0.9.x stable line as supported.

How Has This Been Tested?

• git diff --check
• A targeted Python check verified that the major/minor line in crawl4ai/__version__.py has a supported row in SECURITY.md.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• N/A — this documentation-only change has no code requiring comments
• I have made corresponding changes to the documentation
• N/A — no unit-testable runtime behavior changed
• N/A — the targeted documentation checks pass; existing unit tests are unaffected