When build the docs for debian package, it uses a sphinx building
helper, which does a sanity check for the output.
The sanity check complains missing data-url_root attribute in the
js tag. So this patch changes the js tag to use the same function like
the origin basic theme, which adds additional information like
data-url_root.
Ref: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=997437
e6d5059cbb