Add <model-viewer> HTML tag for a simple 3D model viewer

[torrinworx]

I reccommend adding the ability to call the HTML tag , information on the tag can be found here: https://modelviewer.dev/

This repository is maintained by Google and is very reputable: https://github.com/google/model-viewer

But in short, you could upload a 3D model file like .glb to a repository, then display and interact with it in any README.md file.