Implement greeting message upon issue closure

[thevijayshankersharma]

Description

This PR implements a feature to automatically post a greeting message upon the closure of an issue in the project's tracker system. The message acknowledges the closure and thanks the contributors involved, enhancing the collaboration experience.

Related Issues

Fixes #171

Changes

List the detailed changes made in this PR.
Added new functionality to detect issue closure events.
Implemented logic to generate a greeting message upon closure.
Included a customizable template for the greeting message.
Updated documentation to explain the new feature.

Testing Instructions

Detailed instructions on how to test the changes. Include any setup needed and specific test cases.

Pull this branch.
Ensure the latest dependencies are installed.
Close a test issue.
Verify that a greeting message acknowledging closure appears on the issue page.
Check the formatting and content of the message.

Screenshots (if applicable)

Add any screenshots that help explain or visualize the changes.

Additional Context

This PR aligns with the feature request outlined in issue #171.
The greeting message is designed to enhance user experience and encourage community engagement post-issue resolution.

Checklist

Make sure to check off all the items before submitting. Mark with [x] if done.

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I am working on this issue under GSSOC

[github-actions]

Thank you for submitting your pull request! 🙌 We'll review it as soon as possible. In the meantime, please ensure that your changes align with our CONTRIBUTING.md. If there are any specific instructions or feedback regarding your PR, we'll provide them here. Thanks again for your contribution! 😊