Add tooltip

lib/src/widgets/toolbar/buttons/font_size_button.dart

@@ -156,7 +156,9 @@ class QuillToolbarFontSizeButtonState
               onPressed: _onPressed,
               icon: _buildContent(context),
             )
-          : RawMaterialButton(
+          : Tooltip(
+              message: tooltip,
+              child: RawMaterialButton(
                 visualDensity: VisualDensity.compact,
                 shape: RoundedRectangleBorder(borderRadius: borderRadius),
                 elevation: 0,
@@ -165,6 +167,7 @@ class QuillToolbarFontSizeButtonState
                 onPressed: _onPressed,
                 child: _buildContent(context),
               ),
+            ),
     );
   }