Add CLI commands

[just-victor]

Is there an existing feature request for this?

• I have searched the existing open and closed issues

Feature description

As a user with many short footages, I want to automatize OSD overlay process, for that:

Would be good to have the ability to start the overlay process without a GUI, only by CLI command e.g.
walksnail-osd-tool --video=path/to/AvatarG0000.mp4 --osd=path/to/AvatarG0000.osd --font=path/to/user_bf_24_png --output --path/to/output/file.mp4