docs: fix typo in readme (#217)

**What**:
Just a typo in the docs

**Why**:

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**How**:

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**Checklist**:

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- [ ] Documentation N/A
- [ ] Tests N/A
- [x] Ready to be merged

Author: kirillku

README.md

@@ -639,7 +639,7 @@ class TestComponent extends React.Component {
   render() {
     const {count} = this.state
 
-    return <button onClick={() => this.setState({count: count + 1})}>Click to increase: {count}</div>
+    return <button onClick={() => this.setState({count: count + 1})}>Click to increase: {count}</button>
   }
 }