docs: Add Quick Start Example to README

[YuChenLee1115]

Description

Added a Quick Start Example section to the README to help new users get started with MONAI more easily. The example demonstrates basic medical image loading and spacing adjustment.

Changes Made

• Added new "Quick Start Example" section to README
• Included code example for basic image loading
• Added example for image spacing adjustment
• Improved documentation readability

Purpose

This change aims to make MONAI more accessible to newcomers by providing a clear, practical example of basic functionality.

Testing Done

• Verified the markdown formatting
• Tested the code example locally
• Ensured proper integration with existing documentation

[ericspod]

Suggested change

	```python
	import monai
	from monai.transforms import LoadImage, Spacing
	# Load a medical image
	image = LoadImage()(image_path)
	# Resample the image to a specific spacing
	spaced_image = Spacing(pixdim=(1.5, 1.5, 2.0))(image)
	```python
	from monai.transforms import (
	Compose,
	LoadImage,
	ScaleIntensity,
	AddChannel
	)
	# Define transforms for image preprocessing
	transforms = Compose([
	LoadImage(image_only=True),
	AddChannel(),
	ScaleIntensity()
	])
	# Apply transforms to your image
	image = transforms(image_path)

We're updating the website shortly and will be using the example I've suggested here, is that suitable to you for this update? Thanks for the contribution!

[YuChenLee1115]

So good! Thanks a lot for you!

[ericspod]

If you're ok with this you can commit the suggestion yourself through the Github interface then we can approve, otherwise if you wanted to modify what I'd suggest we can review again.