chore(marketing): add settings screenshot

[esphynox]

Summary

• add a new marketing screenshot for the Keyty settings UI
• keep the asset set current for storefront, docs, or release collateral updates

Tests

• tuist generate
• xcodebuild test -project Keyty.xcodeproj -scheme Keyty -destination 'platform=macOS'
• Other: not run; change only adds a marketing image asset

Run project commands from Apps/Keyty.

UI Changes

Attach screenshots or screen recordings for visible UI changes. Write N/A if there are none.

Before	After
N/A	Added Assets/Marketing/KeyboardVisualizer/keyty-settings-demo.png

Documentation

• Updated relevant docs
• No docs needed

Release Notes

N/A