Swapping sub-units of Episode 2

Strictly speaking not necessary, but logic-vise I think swapping "Types of Images" with "Images as a Matrix" could help in the logic of exercise development by first loading and investigating the image data and then explaining the difference.

Locate the Episode 2 lesson source and find the “Types of Images” and “Images as a Matrix” sections. Review their current order and swap them if the lesson structure supports the requested progression; done means the sections appear in the requested order without disrupting the exercises.

Written by the indexing model from the issue text.