feat: add threatmodel extension to community catalog (#2369)

* feat: add threatmodel extension to community catalog

* update timestamp for catalogue freshness

* update timestamp for catalogue freshness

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

* Update README.md

update readme.md with spec-kit-threatmodel

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Co-authored-by: Samal <navia.samal@sap.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>