Add Sokoban Puzzles

[Miserlou]

Ex:

This is a sokoban puzzle. Please solve it. Your solution must be a string of characters, ex: LDURRUDL

+ + + + + + +
+ * - @ - X +
+ + - @ - + +
+ X - - - $ +
+ + + + + + +

* - The player
% - The player on a goal
@ - A box
X - A goal
$ - A box on a goal
+ - A wall
- - An empty position

Configurable sizes and number of boxes for different difficulty levels.

DS-R1 and CGPT-O1 can solve these, but it takes R1 a very long time for the simplest case (five minutes ish.) O1 does it quickly.

Hacked up from this project (MIT). There's still some stuff in there that can be stripped out (particularly the GUI/sprite stuff), but it's all quite intertwined.

[andreaskoepf]

pygame is a larger dependency. Do we have any chance to get rid of it?

[andreaskoepf]

Please add the sokuban solver in the #56 NOTICE.txt issue.

[Miserlou]

Addressed comments. Pygame was more integrated into this project than I expected and made hacking it up a bit annoying. If I were to do it again, I'd probably just ask the robot to write it from scratch, though this library did come with a few solving strategies to play with. It's only a 19M dep, not toooo bad at least.

[andreaskoepf]

replaced by #77