Added BFS according to the format mentioned.

[Santhosh-Vardhan]

Pull Request.

Description

Added Breadth First Search code in basic questions of BFS and added the question in the basicquestions.md file.

Types of changes

• Bug fix (non-breaking change which fixes an issue).
• New feature (non-breaking change which adds functionality).
• Breaking change (fix or feature that would cause existing functionality to change).
• This change requires a documentation update.
• The code follows the code style of this project.
• Documentation has been updated accordingly.
• Tests have been added to cover the changes.
• All new and existing tests passed.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented on my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

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