feat: workflow for auto validate and assign issues to requested contributor

[vedant-jain03]

This is GitHub action for validating and assigning issues to the contributor.

Validations:

• If the issue is approved by maintainers and removed pending triage label from issue.
• If the issue is not assigned.
• Finally, assign to requested contributor.

Actions:

• Need to comment /assign in the issue.

This issue is much needed:

• Maintainers are not active everytime, this make things automated.
• The contributor who comes first got assigned, and make contributions valid.
• Make process automated and unbiased.

Depends on https://github.com/CircuitVerse/Interactive-Book/pull/644

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