Update all snippets to new format

snippets/Slider.md

@@ -1,4 +1,7 @@
-### Slider
+---
+title:  Slider
+tags: input,beginner
+---
 
 Renders a slider element that uses a callback function to pass its value to the parent component.
 
@@ -21,7 +24,3 @@ function Slider({ callback, disabled = false, readOnly = false }) {
 ```jsx
 ReactDOM.render(<Slider callback={val => console.log(val)} />, document.getElementById('root'));
 ```
-
-<!-- tags: input -->
-
-<!-- expertise: 0 -->