Add lightweight ViT

[gau-nernst]

For learning purpose

• [x] ViT: https://arxiv.org/abs/2010.11929
• [x] MLP-Mixer: https://arxiv.org/abs/2105.01601
• [x] DeiT: https://arxiv.org/abs/2012.12877
• [x] DeiT-III: https://arxiv.org/abs/2204.07118
• [x] CaiT: https://arxiv.org/abs/2103.17239
• [x] Swin: https://arxiv.org/abs/2103.14030
• [ ] Swin V2: https://arxiv.org/abs/2111.09883
• [ ] MobileViT: https://arxiv.org/abs/2110.02178
• [ ] MobileViTv2: https://arxiv.org/abs/2206.02680
• [ ] MobileViTv3: https://arxiv.org/abs/2209.15159
• [x] ConvNeXt: https://arxiv.org/abs/2201.03545
• [x] ConvNeXt-V2: https://arxiv.org/abs/2301.00808
• [ ] TinyViT: https://arxiv.org/abs/2207.10666
• [ ] MobileOne: https://arxiv.org/abs/2206.04040
• [ ] EfficientViT: https://arxiv.org/abs/2305.07027
• [ ] GC ViT: https://arxiv.org/abs/2206.09959
• [ ] Fast ViT: https://arxiv.org/abs/2303.14189
• [ ] Faster ViT: https://arxiv.org/abs/2306.06189
• [ ] MaxViT: https://arxiv.org/abs/2204.01697

Probably will port weights.