FR: support a configuration file like `bibtex-tidy.yaml`

[chrisgrieser]

Right now, I am using bibtex-tidy with a long list of options. Other formatters usually support a config file at the working directory or passed via --config, where you can set your preferred options.

[FlamingTempura]

Nice idea! Can't promise a date, but I'll try to include it in my next batch of work on bibtex-tidy.