Provide specific developer instructions for this repository

[redeboer]

This repository has some peculiarities that not explained by the general develop page. Some things that need explaining (potentially on the general page as well):

• What does environment.yml do, and where does it fetch (optional) pip dependencies and constraints
• What is the first notebook cell in each notebook
• Why are the pip install package==0.x.x statements needed
• How best to work with cell metadata
• How to 'freeze' cell output once a report is finished
• How to store embed images in the notebooks without committing them to the repository (see this tip).
• How to create GIF animations (see #129 (comment))
• ...