Adding Task Transform Tutorial

[nightlessbaron]

Fixes #122

Added a tutorial named "Demystifying Task-Transforms" explaining the l2l.data module.

Notebook version of the tutorial is here

Updated changelog.

[seba-1511]

Thanks a lot @nightlessbaron, this looks great and looks ready to merge.

Before I merge it, I have to update the docs generation pipeline since a few dependencies have become obsolete. I’m working on it now.

[seba-1511]

@nightlessbaron, I've replaced pydoc-markdown with mkdocstrings. In the process I've also cosmetically edited the tutorial so it looks better (eg, shorter section titles).

To see what it looks like, the following should work:

pip install -r requirements-dev.txt
make docs
# open your browser at localhost:8000

Please let me know if everything looks good, then we can merge and deploy the new website.

[nightlessbaron]

@seba-1511, this is looking good. Thanks for this.
Just a minor question - the latex symbols are not rendered. Do I need to replace $$ with [ ] ?
I think we are good to go :)