Feature request: support the AR and LN properties of the SGF standard

[Trevoke]

Hi!

The SGF standard has markups for arrows (AR) and lines (LN) and it would be very very helpful to be able to use those when I create game reviews, to convey information more concisely than through words in the comments (e.g. arrows for ladders or direction of play, lines for sector lines, things like that).
https://www.red-bean.com/sgf/properties.html#AR
https://www.red-bean.com/sgf/properties.html#LN

It would be great to have a client who supports the entire SGF range of markup tools!