v0.8.0

Sparklines are here! Each rectangle now shows a mini chart of historical data.

• Enabled by default - to disable, add sparkline.show: false to your config
• Configurable time periods: 12h, 24h (default), 7d, or 30d
• Works with entity sensors (uses HA long-term statistics) and JSON mode (uses data array from attribute)
• Fully customizable line and fill styles via CSS
• Climate entities: Shows temperature history with HVAC actions (heating/cooling periods)

Major performance overhaul:

• Render multiple cards with hundreds of rectangles without breaking a sweat
• Runs smoothly on low-end devices like Raspberry Pi
• Added performance regression tests to keep the bar high

Other improvements:

• Icons now adapt to background color for better readability (same as labels)
• Config cleanup: use attribute everywhere (old param still works)