Add Emerald Synth — synthwave dark theme

[malleroid]

Description

A synthwave-inspired dark terminal color scheme with deep purple backgrounds and cyan-green accents.

Design principles

• Deep purple base — Background #0d0221 provides a rich, immersive dark canvas
• Cyan-green accent — Primary accent #00ffcc as the signature color
• WCAG contrast — All foreground colors designed to meet AA (4.5:1+), bright black raised to CR≈3.10 for comment readability
• Hue separation — ANSI blue shifted to H231 (30° from bg), cyan to H187 (19° from green) to avoid color collisions on the purple background

More details: https://github.com/malleroid/emerald-synth

New Theme

Submitted as Emerald Synth.yml in YAML format.