Add Flatiron notebooks training notebooks

[oruebel]

The training materials for Pynapple and Nemos use NWB files and are a nice example for applying the tools. These training materials should be added as links in the Pynabpple tools section. In addition, we could also add them to the Data Analysis & Reuse section in the community gallery

• Exercise notebooks: https://flatironinstitute.github.io/ccn-software-fens-2024/generated/for_users/
• Notebooks with code exercises completed: https://flatironinstitute.github.io/ccn-software-fens-2024/generated/just_code/
• Setup instructions and binder: https://flatironinstitute.github.io/ccn-software-fens-2024/