Add piano-keys sounds

[WinnyChang]

Pull Request

Type of Change

• Bug fix
• New feature
• Sound contribution
• Configuration contribution
• Documentation update
• Other (specify)

Description

Add piano key sounds ranging from C3 to E5, including both white and black keys.

Related Issue

Related to #2.

Changes Made

• Created a new folder piano-keys under assets/sounds/.
• Added 29 piano key sound files to the piano-keys folder.
  (Note: filenames for sharp keys use “s” instead of “#” due to kebab-case naming restrictions.)

For Sound Contributions

• Sound is in MP3 format
• File size is under 500KB
• Added sound to assets/sounds/
• Created/updated config that uses the sound

Audio

Audio samples were downloaded from this source, converted from .sf2 to .mp3, trimmed, faded out, and volume-adjusted.

Checklist

• My code/contribution follows the project guidelines
• I have tested my changes
• I have updated documentation as needed
• My changes don't break existing functionality