CCSUBS meet-up at NAB 2024

Beta support for EBU STL added to ttconv. Convert STL to IMSC and SRT. Thanks to Andreas Tai for the hard work and David Ronca for the continued support. Time to kick the tires. #WebVTT is next. https://github.com/sandflow/ttconv/releases/tag/1.0.3b1 #imsc #srt European Broadcasting Union #subtitles #captioning #accessibility