Modify to override operator[] into xml_node

Currently, users can add xml_node by calling append_child(). If
repeatedly insert xml_nodes, operator[] may be more useful than using
this function.
This commit modifies to override operator[] to make appending xml_node
more useful. In additional, this operator inserts a new element with
that key and returns a reference to its mapped value. Notice that this
always increases the xml size by one, even if no mapped value is
assigned to the element.

Signed-off-by: Jihun Ahn <jhun.ahnn@gmail.com>

src/pugixml.cpp

@@ -5496,6 +5496,11 @@ namespace pugi
 		return (_root >= r._root);
 	}
 
+	PUGI__FN xml_node xml_node::operator[](const char_t* name_)
+	{
+		return append_child(name_);
+	}
+
 	PUGI__FN bool xml_node::empty() const
 	{
 		return !_root;

src/pugixml.hpp

@@ -488,6 +488,8 @@ namespace pugi
 		bool operator<=(const xml_node& r) const;
 		bool operator>=(const xml_node& r) const;
 
+		xml_node operator[](const char_t* name_);
+
 		// Check if node is empty.
 		bool empty() const;