encoding/xml: empty namespace conventions are badly documented #11735
Description
During the discussion in #11724 @rogpeppe wrote:
The existing Go convention is that if no namespace is specified in the struct tag, it will match any namespace including the empty namespace.
But the package docs don't seem to mention that. This behaviour should be documented better, because a lot of people will assume that xml:"name,attr" will match name="foo" but not ns:name="bar".