Add Puri (Chess Game) as an optional Package

[cipri]

I was thinking that perhaps my chess game could be added as an optional package, since it's working not so bad.
At least it could be added to the optional packages for the nightlies, so that it can be tested, and seen if it should remain in the optional packages for alpha4.

And perhpas the name of the optional package should be something like PuriChess? so that it's clear that it's a chess game.

the bep file was already added in a previous ticket, and it's working fine. The optional package is also created without any problems.

[scottmc]

added to Haiku a few months ago.