Feature Request: Add Mish activation

[digantamisra98]

Mish is a new novel activation function proposed in this paper.
It has shown promising results so far and has been adopted in several packages including:

• TensorFlow-Addons
• SpaCy (Tok2Vec Layer)
• Thinc - SpaCy's official NLP based ML library
• Echo AI
• CNTKX - Extension of Microsoft's CNTK
• FastAI-Dev
• Darknet
• Yolov3
• BeeDNN - Library in C++
• Gen-EfficientNet-PyTorch
• dnet

All benchmarks, analysis and links to official package implementations can be found in this repository

It would be nice to have Mish as an option within the activation function group.

This is the comparison of Mish with other conventional activation functions in a SEResNet-50 for CIFAR-10: (Better accuracy and faster than GELU)

[raver119]

Implemented and merged.

[AlexDBlack]

And thanks for the detailed feature request @digantamisra98
It should be up on snapshots within a few days (once we merge back) and of course the next release (which we are working towards at present).

[digantamisra98]

@AlexDBlack Thanks for considering the request. Looking forward to the release.