Use Labels for Heredoc-like Sections

[puria]

As a developer, I want to use labels to specify start and end keywords for commenting sections so that I can handle heredoc-like structures.

Example:
tgcom --file main.go --start-label START --end-label END --action comment

[FilippoTrotter]

@puria until now, I've added the option for labels only in the case of a single file. Should it also be added in the case of multiple files? If yes, how should the command be?