Combine two subtitles into a single file.
Combining two subtitle files is usually used to create multilanguage subtitles.
Multilanguage subtitles are useful when studying a new language.
Merging subtitles can also be useful when your subtitles wrongly assume that the video has hard-coded subtitles for parts where a foreign language is spoken,
you can then merge subtitles for the foreign language into the original subtitle file.
This tool requires two files, a base file and a merge file.
The merge file will be merged into the base file.
The format of the base file will not be changed.