Add error boundary to save Slate from a crash on corrupt DOM (#2792)

* Working version of restore dom

* Fix linting errors

* Add button to corrupt DOM

* Added error boundary that fixes DOM on render error

* Fix linting errors

* Fix debug output for componentDidCatch

* Improve example by adding a separate restoreDOM button

* Remove key change from error boundary which is not necessary

* Fix linting error

packages/slate-react/src/components/content.js

@@ -75,6 +75,22 @@ class Content extends React.Component {
     tagName: 'div',
   }
 
+  /**
+   * An error boundary. If there is a render error, we increment `errorKey`
+   * which is part of the container `key` which forces a re-render from
+   * scratch.
+   *
+   * @param {Error} error
+   * @param {String} info
+   */
+
+  componentDidCatch(error, info) {
+    debug('componentDidCatch', { error, info })
+    // The call to `setState` is required despite not setting a value.
+    // Without this call, React will not try to recreate the component tree.
+    this.setState({})
+  }
+
   /**
    * Temporary values.
    *