• Support more subtitle formats, including SAMI (.sami, .smi) and EBU STL (.stl)
• Add the docker builds for Fedora and Debian
• Allow alignment against embedded subtitles using selectors
  • embedded:page_num for DVB Teletext
  • embedded:stream_index for Matroska
• Add subtitle file encoding auto-detection
• Fix XML declarations for TTML files
• Add the subaligner_convert CLI for subtitle conversion
• Make the ffmpeg/libav path re-configurable via env var FFMPEG_PATH