feat: add issue approval workflow

[Manancode]

This PR covers what discussed here [FEATURE] Modify Github Bot to review & close Spam Issues/PRs. For maintainers please refer this detailed description. This PR is tested locally e2e (see images attached for ref)

this is the current flow

New Issue Created:
Automatically labels issue with needs-approval
Posts welcome comment explaining the approval process and timeline
Maintainers and bots are exempted (no approval needed)

Maintainer Approval/Rejection:
Maintainers comment /approve to approve the issue
Maintainers comment /reject to reject and close the issue
Only users with write/admin permissions can use these commands
Approved issues get approved label, needs-approval label is removed

Automated Reminders & Closure:
After 7 days: Posts reminder comment if issue still needs approval
After 21 days: Automatically closes issue if not approved

Pull Request:
PRs that reference unapproved issues (like fixes #, closes #) are automatically closed
Standalone PRs (with no linked issues) are allowed
PRs from maintainers are allowed

Reopened Issues:
When an issue is reopened, needs-approval label is re-added automatically
Approval cycle restarts

[github-actions]

Welcome to AsyncAPI. Thanks a lot for creating your first pull request. Please check out our contributors guide useful for opening a pull request.
Keep in mind there are also other channels you can use to interact with AsyncAPI community. For more details check out this issue.

[princerajpoot20]

FYI: asyncapi/website#3742 (comment)
It is not ready for review. The design is yet to be finalized.

[princerajpoot20]

/dnm