v0.9.27

NNlib v0.9.27

Diff since v0.9.26

Merged pull requests:

• Fix NaN gradient in spectrogram (#617) (@pxl-th)
• Use return_type not _return_type to fix an error on nightly (#618) (@mcabbott)
• Add unthunk in conv.jl (#620) (@mcabbott)

Closed issues:

• Test failures with Zygote 0.7 (#619)