⚡ Repository standardization

Hi @NicTanghe, we need to adjust a few things first to move forward, ok? ✨

First, we need to update the screenshot!

Can you take a single capture at the closest possible resolution to 1728x1117?

We also need a separate `.md` with installation instructions to show the theme on the site.

I ask for these changes to standardize with the other repositories, [see an example](https://github.com/dracula/notepad-plus-plus); this is also important because it helps other potential users who would like to contribute too! 😁

Let me know if something isn't possible or if you have any questions! 🙂