Add support for Polish scale (Kurtyka scale)

[Agilulfo]

This scale is used in Poland for sport and trad climbs
see: https://en.wikipedia.org/wiki/Grade_(climbing)#Polish

[musoke]

Would you like to work on this?

[Agilulfo]

I don't speak typescript but having given a look at the changes to add the Brasilian scale I think I can pull it off with a little help in the code review.

[Agilulfo]

@musoke I've pushed #173.

Am I on the right path? (see missing steps in PR description TODO list)

out of curiosity.. why is the data on grades duplicated? (there are both json and csv files.)

[musoke]

out of curiosity.. why is the data on grades duplicated? (there are both json and csv files.)

Looks like you worked it out, but since you asked: the CSV is for human editing and the JSON is automatically generated from it.