docs: update security policy for ISO 27001

[wrpeck]

Status

*Ready

Description

Updated our security policy to align with our ISMS policy (needed for ISO 27001 audit and certification). The changes are pretty minor:

• Updated internal tracking mechanisms for Incidents
• Updated our third-party assessment to include internal and external audits for ISO 27001 compliance
• Updated the reviewed date

[wrpeck]

Tagging @eseidel for review

[AbhishekDoshi26]

Looks good. The date, incident tracking, and third-party assessment updates match what the description says, and nothing else on the page contradicts them.

I pushed f1a59fb to get CI green:

• spell-check: cspell checks the PR title, and Wrpeck in the branch-derived title failed. I retitled the PR to docs: update security policy for ISO 27001.
• build (Prettier): the two edited paragraphs were longer than 80 columns and one had trailing whitespace. They're now reflowed.
• Wording: "per the Incident Response Policy" referred to a document readers can't see, and the paragraph above calls it a "private playbook". It now reads "tracked according to Shorebird's internal Incident Response Policy" so it's clear the policy is internal.

All checks pass now.