Add `link_id` and it's description

[divyabhushan]

Description

Motivation and Context

Slack channel #help-cloud-ngfw discussion by Stakeholders

How Has This Been Tested?

Screenshots (if appropriate)

Types of changes

• doc change

Checklist

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

[divyabhushan]

@migara @panw-ppalkar Please review and merge.