gnodraw/v0 package

Package gnodraw is a pay-per-pixel collaborative canvas: anyone can paint any pixel of a Width x Height grid in one of 15 colors by sending exactly Price() ugnot per pixel along with the call. Pixels can be repainted by anyone, for the same price. Payments are forwarded to the admin wallet as they arrive, and the admin paints for free.

The grid logic lives in gno.land/p/g1v7s3j506wqul2zwt90awgjphpx4ztwga0926f7/canvas/v0; this realm adds the payment guard, the owner controls and the read API used by the web client.