Add Social Preview to GitHub Settings

### Describe the bug

## Description
We currently have the default unfurl GH thing happening and it should be better, so let's do that.

See https://github.com/infinitered/nsfwjs/settings for an example

### Reactotron version

n/a

Start by comparing the repository's GitHub settings with the example at https://github.com/infinitered/nsfwjs/settings, focusing on the current default unfurl behavior. The issue names no source file or test; done means the Reactotron repository has an improved social preview configured and its rendered preview can be verified.

Written by the indexing model from the issue text.