TextEditor: Fix commenting shortcut `<Ctrl-/>`

When you select a text area in "bottom-up" way (e.g. from line 10
to line 5), then type the shortcut, the text editor will not
comment those text for you.

Normalize the text range can easily fix this minor bug.

Userland/Libraries/LibGUI/TextEditor.cpp

@@ -1022,7 +1022,7 @@ void TextEditor::keydown_event(KeyEvent& event)
         if (m_highlighter != nullptr) {
             auto prefix = m_highlighter->comment_prefix().value_or(""sv);
             auto suffix = m_highlighter->comment_suffix().value_or(""sv);
-            auto range = has_selection() ? selection() : TextRange { { m_cursor.line(), m_cursor.column() }, { m_cursor.line(), m_cursor.column() } };
+            auto range = has_selection() ? selection().normalized() : TextRange { { m_cursor.line(), m_cursor.column() }, { m_cursor.line(), m_cursor.column() } };
 
             auto is_already_commented = true;
             for (size_t i = range.start().line(); i <= range.end().line(); i++) {