feat: transcode dcm to output stream

[adrianog3]

Hello Nicolas, I propose to overload the dcm2dcm method in Transcoder class to allow writing data directly to an OutputStream.

This parameter is very important for my use case, because I do the reading dcm files in a certain transfer syntax, and I send it through the http protocol using another transfer syntax, so generating files is costly and unnecessary.

[nroduit]

Thank you for this proposal which seems to me OK