README: Add note about ScanElement

Signed-off-by: Maxime “pep” Buquet <pep@bouah.net>

README.md

@@ -49,11 +49,27 @@ This library supports parsing the following:
 	Optional lines starting with a `#` or `//` and ending with a newline
 	(`\n`). They get discarded in the output
 
-## minidom::Element
+## ScanElement
 
-Minidom `Element`s require every element to be namespaced. This parser adds
-`jabber:client` as a default namespace. It also adds a `scansion` namespace
-that is used for the `scansion:strict` XML parameter.
+`ScanElement` is a wrapper to `minidom::Element` that reimplements
+`PartialEq`. Most checks will happen in there, variables in attributes will
+also be read at this time.
+
+`PartialEq` is only implemented for `Element` as it wouldn't make sense to
+compare two `ScanElement`s.
+
+This interface may change in the future as it doesn't allow returning a Result
+(errors may happen when parsing variables: missing from context, etc.).
+Currently when a referenced `client` doesn't exist in context, the comparison
+fails. If no context has been specified, comparison will go on, skipping
+variable handling.
+
+`minidom::Element` requires every element to be namespaced and `ScanElement`
+has no special treatment for this. Be sure to include namespaces in your
+`Element`s. You may want to use `Element::from_reader_with_prefixes`.
+
+Namespaced attributes aren't yet handled by minidom so `scansion:strict`
+also isn't treated in any special way.
 
 # Reporting bugs