Documentation for building custom pos_patterns is needed

[n-splv]

Hi! Thanks for the awesome library.

After failing miserably to repeat the PoS pattern from your paper, I thought that it might be a good idea to share some instructions, e.g. what is the difference between <N.> and etc.

Also a discussion may be started, where people would share useful PoS patterns they discovered for different languages.
Cheers!