[PL-Doc] OPA policy documentation for Service account

[ivikramsahu]

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Description

• Please describe your changes: New page added under governance → policy as code → OPA for service account
• Jira/GitHub Issue numbers (if any): PL-60496
• Preview links/images (Internal contributors only): __________________

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[bot-gitexp-user]

Please check the Execution Link of the Pipeline for the Website Draft URL. This is located in the Preview Step behind the Harness VPN and also is available in #hdh_alerts. E.g Website Draft URL: https://unique-id--harness-developer.netlify.app. Current Draft URL is: https://67b21179a306b892b79d8e59--harness-developer.netlify.app