Missing link to Relax NG in Develop > Extensions (website)

Summary:

I'm looking for a schema definition for the Inkscape extension http://www.inkscape.org/namespace/inkscape/extension namespace. It looks like it used to be linked on https://inkscape.org/develop/extensions/#user-interface-and-parameter-types-extension-definition-file-inx, but now there's only a available [here] (where "here" is not a link).