📃 Added placeholder to docs

Author: aromalanil

README.md

@@ -75,6 +75,13 @@ export default class App extends Component {
     <td>''</td>
     <td>The value of the OTP passed into the component.</td>
   </tr>
+  <tr>
+    <td>placeholder</td>
+    <td>string</td>
+    <td>false</td>
+    <td>none</td>
+    <td>Provide a custom placeholder. Should be a single character or a string of length <code>&lt;numInputs&lt;</code>.</td>
+  </tr>
   <tr>
     <td>separator</td>
     <td>component<br/></td>