LibWeb: Add support for range deletion.

Author: https://github.com/asynts
Commit: 43dc47a494
Pull-request: https://github.com/SerenityOS/serenity/pull/4318
Reviewed-by: https://github.com/Lubrsi
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/linusg

Libraries/LibWeb/DOM/Position.cpp

@@ -39,6 +39,24 @@ Position::~Position()
 {
 }
 
+Range Range::normalized() const
+{
+    if (!is_valid())
+        return {};
+
+    if (m_start.node() == m_end.node()) {
+        if (m_start.offset() <= m_end.offset())
+            return *this;
+
+        return { m_end, m_start };
+    }
+
+    if (m_start.node()->is_before(*m_end.node()))
+        return *this;
+
+    return { m_end, m_start };
+}
+
 const LogStream& operator<<(const LogStream& stream, const Position& position)
 {
     if (!position.node())