add the exam chatbot feature

[agarwalhimanshugaya]

Description

1. I implement the chatbot feature
2. It reply user according to the user question

Resolves: #280

Checklist

Before submitting this pull request, kindly verify that the ensuing checkpoints have been reached.

• [x] Have you adhered to the repository's defined coding convention rules?
• [x] Have you updated the 'documentation.md' file with the method/function documentation?
• [x] Have you sent a message along with the result or response?
• [x] Have you used the try-catch technique?
• [x] Has the method/class been added to the documentation (md file)?

Screenshots

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Additional Notes/Comments

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I certify that I have carried out the relevant checks and provided the requisite screenshot for validation by submitting this pull request. I appreciate your contribution.

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[agarwalhimanshugaya]

@hereisSwapnil sr kindly review my pr because after 31st july it is not counted for gssoc