S (white space) consists of one or more space (#x20) characters, carriage returns, line feeds, or tabs.
White Space
[3] | S | ::= | (#x20 \| #x9 \| #xD \| #xA)+
-- | -- | -- | --
Note:
The presence of #xD in the above production is maintained purely for backward compatibility
with the First Edition. As explained in 2.11 End-of-Line Handling, all #xD characters literally
present in an XML document are either removed or replaced by #xA characters before any other
processing is done. The only way to get a #xD character to match this production is to use a
character reference in an entity value literal.
Support whitespace as nodes as a precursor to whitespace preservation support
https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-S