Premiere Pro: add Sequence.createCaptionTrack and related CAPTION_FORMAT constants

[myselfhimself]

Hello,

just drafted a pull request for https://ppro-scripting.docsforadobe.dev/sequence/sequence.html?highlight=createcaptiontrack#sequence-createcaptiontrack

#124

I did not know if that API endpoint pre-existed before 15.0

I have to test those still.. It is unsure whether the underlying caption format constants map to class static attributes Sequence. and typed as number.