Missing p2 configuration in all recent update sides

[a-sr]

An error was reported to me regarding installation of Klighd plugins. Eclipse was accessing https://kieler.github.io/KLighD/v2.0.0/content.xml and got a connection error that prevented installation.

I checked the update site and there is no content.xml but only content.xml.xz which is correct but the p2.index does only list content.xml and not content.xml.xz (https://github.com/kieler/KLighD/blob/gh-pages/v2.0.0/p2.index).
According to https://wiki.eclipse.org/Equinox/p2/p2_index#New_in_Mars_Release:_XZ_Example_for_simple_repository the p2.index should list both in oder to be fully compatible to new eclipse versions.

I think this problem did not occur earlier because eclipse usually falls back to using content.jar but I guess this did not happen in this case. Nonetheless, if content.xml.xz is provided, it should be listed.