v2.1.0 - Imsak and Duha Support

What's New in v2.1.0

✨ New Features

• Imsak Time - Calculate fasting start time with configurable buffer before Fajr
• Duha Time - Calculate forenoon prayer time based on sun elevation angle

📋 API Changes

• Added setImsakOffset(minutes) - Default: 10 minutes before Fajr
• Added setDuhaAngle(degrees) - Default: 4.5° above horizon
• PrayerTimesResult now includes imsak and duha fields
• Legacy API supports optional Imsak/Duha output parameters

📚 New Example

• Imsak_Duha_Example.ino - Multi-city test with regional variations

🙏 Thanks

Requested by @karbyt in #2