Add explanatory comments to baked LUTs.

LUTs don’t usually contain any information (other than possibly in the name) about the transform they apply, and the input and output colour encoding. If `ociobakelut` added a comment line to the LUT giving the parameters used to create it, it could be very helpful to subsequent users of that LUT.

Start at the ociobakelut entry point and trace how baked LUT output is written. Determine where the LUT comment line can include the creation parameters and input/output colour encoding; done means generated LUTs contain that explanatory information.

Written by the indexing model from the issue text.