The Reference link in the Extras dropdown menu links to Key Points, not to actual references

[allegravia]

We need to change the current reference.md to auto-populate with references from episodes, instead of with Key Points (as it is now).
To this aim, we should:

• add references in episode headers
• move current reference.md content to, e.g., key-point.md
• create an item ("Key Points") in the Extras dropdown menu pointing to key-point.md
• modify current reference.md so that it auto-populates with references from episode headers