Revert changes that delete MoCo

Hi everyone,

Could you please revert the changes from the [Commit 8976944](https://github.com/facebookresearch/moco/commit/8976944da9c6b94cbd9158d7ebe50912aef807ef) for this repository? The rationale is that this page was the official implementation of [the MoCo paper by K He et al](https://openaccess.thecvf.com/content_CVPR_2020/papers/He_Momentum_Contrast_for_Unsupervised_Visual_Representation_Learning_CVPR_2020_paper.pdf) (cited around 20K times). The paper still refers to this github repo. So, could it be restored, and ideally protected from being removed?

The git history for the repo is, of course, still available, but seems to be at risk, too.