Fix parser default from _handler to func

[Andfreitag]

@dvm-shlee

In src/brkraw_cli_addon/plugin.py, the line:

parser.set_defaults(_handler=_run)

should be changed to:

parser.set_defaults(func=_run)

This change aligns with line 125 in
brkraw/src/brkraw/cli/main.py:
https://github.com/BrkRaw/brkraw/blob/main/src/brkraw/cli/main.py

Reference snippet:

if not hasattr(args, "func"):
    parser.print_help()
    return 2

Using _handler caused issues on my setup, for example, I could not actually use the function foo.
I'm not completely sure about the full structure, but this quick fix worked perfectly for me in the terminal.
I did not submit a pull request as I am not confident about the overall structure and potential side effects.

I also want to say that I’m genuinely impressed with the whole BrkRaw project rework!