Description

The iframes sources are defined ashttps://whatever.readthedocs.io/lite/replite/..., "lite" being the directory in which JupyterLite is built.
This causes an issue when the iframe is embedded in a docs sub-directory, as the iframe link would append the directory to the URL:https://whatever.readthedocs.io/subdir/lite/replite/... resulting in a 404 issue.

I tried fixing this in#32, which was working just fine in some cases. But it seems to have broken the jupyterlite-sphinx docs as reported by@psychemedia in#34

This fix was reverted for now, in#35, but I believe we should find a way to fix the sub-directory issue mentioned above.

We probably need to be smart about the URL of the iframe, trying to find thelite path relatively to the the sub-directory that's calling the directive.