add format sami = smi

[milahu]

sami is a rarely-used subtitles format, which looks like broken html (unclosed tags)

https://en.wikipedia.org/wiki/SAMI

https://github.com/LinearAlpha/smi2ass/blob/main/smi2ass.py - hacky... fighting the html parser

https://github.com/xbmc/xbmc/blob/master/xbmc/cores/VideoPlayer/DVDSubtitles/DVDSubtitleParserSami.cpp

https://github.com/videolan/vlc/blob/master/modules/demux/subtitle.c#L1380 - static int ParseSami

i would implement this as an xml html stream parser, to handle all the unclosed tags
and because we dont need the html dom - we build our own "document"