Update CONTRIBUTING.md

[wwzeng1]

Hi! This PR was copied from https://github.com/sweepai-dev/convoy/pull/3 generated by https://github.com/sweepai/sweep

Description

This PR adds guidelines for raising issues to the CONTRIBUTING.md file. The new guidelines provide instructions on how to provide detailed descriptions when raising issues, improving the quality and clarity of the issues raised.

Changes Made

• Added a new section titled "Guidelines for Raising Issues" to the CONTRIBUTING.md file.
• Included instructions on providing a clear and concise title, a detailed description of the issue, steps to reproduce the issue, expected and actual results, and any relevant error messages or logs.
• Added a template for users to follow when creating new issues.

Fixes #1505

[CLAassistant]

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