feat: support React.Component in marks

examples/marks.js

@@ -7,7 +7,7 @@ const Slider = require('rc-slider');
 const style = {width: 400, margin: 50};
 const marks = {
   '-10': '-10°C',
-  0: '0°C',
+  0: <strong>0°C</strong>,
   26: '26°C',
   37: '37°C',
   50: '50°C',
@@ -15,7 +15,7 @@ const marks = {
     style: {
       color: 'red',
     },
-    label: '100°C',
+    label: <strong>100°C</strong>,
   },
 };