Add integration with HF Hub

[qubvel]

Description

Hi! Amazing repo!

I made a draft with PytorchModelHubMixin for a few models in the repo. This mixin adds a few methods to make it possible to save/load models and share them with the HF hub.

Here is a short example:

from monai.networks.nets import AHNet

net = AHNet()

# save to a local folder
net.save_pretrained("qubvel-hf/ahnet")

# push to HF hub
net.push_to_hub("qubvel-hf/ahnet")

# load form local folder or HF hub
net = AHNet.from_pretrained("qubvel-hf/ahnet")

I believe the repo and community may benefit from sharing pretrained models built with this framework! Let me know if it aligns with your roadmap, I will be happy to help you with implementation or to complete the PR!

Types of changes

• [x] Non-breaking change (fix or new feature that would not break existing functionality).
• [ ] Breaking change (fix or new feature that would cause existing functionality to change).
• [ ] New tests added to cover the changes.
• [ ] Integration tests passed locally by running ./runtests.sh -f -u --net --coverage.
• [x] Quick tests passed locally by running ./runtests.sh --quick --unittests --disttests.
• [ ] In-line docstrings updated.
• [ ] Documentation updated, tested make html command in the docs/ folder.