GitHub PR images comparer

If you are like me and don't like to play "Find 5 differences" in your GitHub PR images, then this extension is just for you. Because:
- It adds additional image comparer to the GitHub PR file preview that shows what pixels changed so you can easily spot the difference.
- You can open original, changed and diff images in a preview dialog for better comparison.
- There is also settings menu that allows you to make this comparer as a default one and change the threshold.

Changelog
0.4.0 - 2022-05-01
- 💄 Private repos support!
- 🐛 Fixed images stretching in width.
- 🐛 Fixed page changes detection in order to show diffs when page changes.

0.3.0 - 2022-04-27
- 💄 Using `IntersectionObserver` to only load images when they are almost in the viewport
- 🐛 Doing nothing in private repos as we don't know how to handle them

0.2.1 - 2022-04-18
- 🐛 Showing diffs in any commit inside PR.
- 🐛 Making the extension work with most popular images extensions.

0.2.0 - 2022-04-18
- 💄 Showing diff images for between changes inside the PR.
- 💄 Added dialog animation.