Update posture api sidebar and intro

[sra-hub]

Description

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes if appropriate.
• All new and existing tests passed.

[github-actions]

Visit the preview URL for this PR (updated for commit 1b2dc66):

https://pan-dev-f1b58--pr1271-6crqqldi.web.app

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