Adds new command to parse a single reference

[mauromsl]

The reference is passed as the sole input argument and the result is printed to stdout.

I've also considered altering the anystyle parse command with a flag declaring to parse the input argument from STDIN instead walking the given path, but this works fine for my purposes. Happy to change it based on your thoughts.

[inukshuk]

This looks really useful, thanks!

I think I'd prefer using a flag for the parse command or maybe even a global flag, if we also add an option to read from stdin.

Using this flag would have to imply --stdout I guess, unless and output argument is given.