Add `Dataset` and `DataLoader`.

[JamorMoussa]

Issue Description: Adding Dataset and DataLoader for neuranet, These classes are fundamental for organizing and managing data efficiently.

1. Dataset Class:

The `Dataset class will serve as an abstract base class, defining a structure for organizing and managing data. It is mandatory for any custom dataset to implement a logic for retrieving elements by index.

2. DataLoader Class:

The DataLoader class will be responsible for creating an iterator over a given dataset. It will handle loading and batching the data, with an additional option to shuffle the data.

class DataLoader:
    def __init__(self, dataset, batch_size=1, shuffle=False):
        ...

    def __iter__(self):
        ....

custom_dataset = CustomDataset()  # Instantiate your custom dataset
loader = DataLoader(custom_dataset, batch_size=64, shuffle=True)

for x, y in loader:
    ...