add square logos

[yochannah]

The current "no text" logos in the various folders are great, but it would be nice to have ones that were square (with whitespace added around the edge as needed) so they don't end up being cropped strangely!

Task

Add additional logos to each folder (model 1, model 2, models 3-4) that have a square aspect ratio, ideally in both png and svg.

1. Comment on this task stating that you intend to complete this task
2. When you're ready, add your files to the relevant directory for each logo model and create a pull request.
3. Bask in glory and email me your address if you'd like to have some codeisscience stickers for your trouble.