Add CNN class for handling MNIST dataset

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Description

This PR adds a new CNN class in the cnn.py file to handle the MNIST dataset. The CNN class is implemented using PyTorch and includes the necessary layers for training on the MNIST dataset. The class also includes a train method to perform the training loop. The main.py file is modified to import the CNN class and call the train method using the MNIST trainloader.

Summary of Changes

• Created a new file src/cnn.py to define the CNN class.
• Imported necessary PyTorch modules in cnn.py.
• Defined the CNN class with an __init__ method to initialize the CNN layers, a forward method for the forward pass, and a train method for training on the MNIST dataset.
• Added docstrings and comments to the CNN class and its methods.
• Modified src/main.py to import the CNN class and call the train method using the MNIST trainloader.
• Added comments to explain the new code.

Please review and merge this PR. Thank you!

Fixes #9.

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Rollback Files For Sweep

• Rollback changes to src/cnn.py
• Rollback changes to src/cnn.py
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