Create a comprehensive README.md for pixelImage & address inconsistent app name casing

[pixelThreader]

Task

Create a comprehensive README.md for the pixelImage app. The README should cover:

• App overview
• Features
• Installation instructions
• Usage examples
• Screenshots (if available)
• Contributing guidelines
• License
• Any other relevant sections typically found in high-quality open source READMEs

Additional Note

There is an issue with the app name: it should be "pixelImage" (with lowercase "p"), but in some places within the app, the name appears as "PixelImage" (with an uppercase "P"). Please note this inconsistency so it can be addressed.