Summary

Fixes loading images within the image timeline, issues were caused by not taking zoom into account
Restores current zoom on page reload + tests
Adds tests for adding/removing image layers

Testing

Enter the browsers and the output modes (minimal, normal, embed) this change was tested

browser	normal	minimal	embed
firefox	tested	tested	tested
chrome	tested	tested	tested
safari	tested	tested	tested
edge	tested	tested	tested