Add Argsfile Support

[XenoAmess]

command line is good but if there be config.json or something that will be better.
I'm trying to make a site to calculate statitics badge using tokei.
But I know nothing about rust and I wanna invoke tokei from commandline, and for safety I think it be better to invoke tokei with a json configuration file instead of too long raw commandline.
thx.

[XAMPPRocky]

@XenoAmess Thank you for your issue! You can provide some options through .tokeirc/tokeirc.toml, I believe there is such a thing as "argfiles" where you can say @args and it will pick up a file called args containing your arguments. Tokei uses a third party library for parsing the CLI (clap-rs), which doesn't support this. I would prefer the implementation for that feature remain outside of tokei, so I'll file an issue with them.