address #28 and #29

start adopting a specific flavor of linear attention that makes a lot…

… of sense

force latest rotary embedding

just use device off the raw audio tensor passed in

window function for stft needs to be set on the correct device

handle multi stft recon loss window fn as well, default to hann

address #24 with better defaults

release fix for number of stems with mel band roformer, thanks to @cr…

…landsc

some hparams for mel band roformer

freq indices precomputed for stereo for mel-band roformer