version 1.19.0 beta 4

What's Changed

• Add simple webapp to play with different parameters by @basnijholt in #715
• Small WebApp improvements by @basnijholt in #716
• Fix min_sunrise_time and max_sunset_time by @basnijholt in #717
• Bump to 1.19.0b4 in manifest.json by @basnijholt in #718

Full Changelog: 1.19.0b3...1.19.0b4