New RIFE_m model

[oblessnoob]

https://github.com/hzwer/arXiv2020-RIFE/blob/main/model/IFNet_m.py

https://drive.google.com/file/d/147XVsDXBfJPlyct2jfo9kpbL944mNeZr/view?usp=sharing

[AIVFI]

Finally we have a new RIFEm for arbitrary-timestep frame interpolation. The progress is enormous. Finally the interpolation results for DAIN and EDSCm have been beaten:

old results: https://arxiv.org/pdf/2011.06294v6.pdf new results: https://arxiv.org/pdf/2011.06294.pdf

HolyWu, please add RIFEm and 4x interpolation to vs-rife.