Add missing element in PHP dark mode styler

Default DarkMode theme style for PHP was missing one element (COMPLEX VARIABLE).
Also Make variables in strings bold so they are more distinguishable.

Close #10502

PowerEditor/installer/themes/DarkModeDefault.xml

@@ -861,7 +861,8 @@ License:             GPL2
             <WordsStyle name="QUESTION MARK" styleID="18" fgColor="7F9F7F" bgColor="3F3F3F" fontName="" fontStyle="1" fontSize="" />
             <WordsStyle name="DEFAULT" styleID="118" fgColor="DCDCCC" bgColor="3F3F3F" fontName="" fontStyle="0" fontSize="" />
             <WordsStyle name="STRING" styleID="119" fgColor="CC9393" bgColor="3F3F3F" fontName="" fontStyle="0" fontSize="" />
-            <WordsStyle name="STRING VARIABLE" styleID="126" fgColor="CC9393" bgColor="3F3F3F" fontName="" fontStyle="0" fontSize="" />
+            <WordsStyle name="STRING VARIABLE" styleID="126" fgColor="CC9393" bgColor="3F3F3F" fontName="" fontStyle="1" fontSize="" />
+            <WordsStyle name="COMPLEX VARIABLE" styleID="104" fgColor="CC9393" bgColor="3F3F3F" fontName="" fontStyle="1" fontSize="" />
             <WordsStyle name="SIMPLESTRING" styleID="120" fgColor="CC9393" bgColor="3F3F3F" fontName="" fontStyle="0" fontSize="" />
             <WordsStyle name="WORD" styleID="121" fgColor="DFC47D" bgColor="3F3F3F" fontName="" fontStyle="1" fontSize="" keywordClass="instre1" />
             <WordsStyle name="NUMBER" styleID="122" fgColor="8CD0D3" bgColor="3F3F3F" fontName="" fontStyle="0" fontSize="" />