Add image to README for visual enhancement

[Gabko14]

Added an image to enhance the README content.

[claude]

Post-Merge Review

This PR adds a screenshot to the README, which is a nice visual enhancement. The change is straightforward and serves its purpose well.

Minor suggestions for future consideration:

1. Alt text: The alt="image" attribute isn't descriptive. A more meaningful alt text like alt="Ghostly app screenshot showing the note-taking interface" would improve accessibility for screen reader users.

2. Fixed dimensions: The hardcoded width="451" height="436" may cause the image to overflow on narrow viewports. Consider using relative sizing or removing explicit dimensions to let the browser handle responsive scaling.

These are minor improvements and don't block anything since the PR is already merged. Overall, adding a visual preview of the app to the README is a good documentation improvement.