【需求】latex居中

@@ -717,7 +717,7 @@ class LatexMath extends InlineMd {
               ),
               ),
             );
             );
     return WidgetSpan(
     return WidgetSpan(
-      alignment: PlaceholderAlignment.baseline,
+      alignment: PlaceholderAlignment.middle,
       baseline: TextBaseline.alphabetic,
       baseline: TextBaseline.alphabetic,
       child: builder(
       child: builder(
         context,
         context,