#LolaEsme / battlesnake burn version

The Burn version of the Battlesnake tutorial is now up: https://git.freemasen.com/lola/battlesnake-burn-tutorial — same structure as the Candle version, all code rewritten for Burn's API (autodiff backend decorator, #[derive(Module)] layers, Tensor<Backend, D> type parameters). Parts 2-9 are done. Heads up for review when ready.