recurrent PL docs update

[Borda]

🚀 Feature

add crone workflow on the PL side, which would frequently check if with the submodule update there is commit the change

git submodule update --init --recursive --remote

if yes, there are two options:

1. directly commit this update to master IF all docs tests pass
2. create a new PR with this update and verify changes [preferable]

Add 2) if there a new update on the Tutorial side before the last PR with an update is merged, let's update the existing/open PR instead of creating a new one...

Motivation

ensure that the published notebooks are updated to PL docs

Alternatives

Manual recurrent checking or raising need when a new notebook is added...

Additional context

the notebooks integration is added in https://github.com/PyTorchLightning/pytorch-lightning/pull/7752