<script src="https://embed.github.com/view/geojson/<username>/<repo>/<ref>/<path_to_file>"></script>
<script src="https://embed.github.com/view/3d/<username>/<repo>/<ref>/<path_to_file>"></script>
For example, if your map's URL is github.com/skalnik/secret-bear-clip/blob/master/stl/clip.stl, your embed code would be:
<script src="https://embed.github.com/view/3d/skalnik/secret-bear-clip/master/stl/clip.stl"></script>
By default, the embedded renderer is 420px x 620px, but you can customize the output by passing height and width variables as parameters at the end, such as ?height=300&width=500
.
Note: ref can be a branch (like master), or the hash to an individual commit (like 2391ae).