Adapt to allow multiple images on each step

This adapts the current scroll set up so that foreground images are now added to an svg canvas. This perfectly overlaps the background image, and character pngs are added to it. I';m using the svg even though these are images, so multiple images can be added, positioned, and scaled within the same space. These attributes have been added to public/assets/text/content.json for each step. This has also been modified to allow multiple images added on top of the background at steps, with unique scaling and positioning for each image.

Current positions and scales are random.