Use autosize to automatically expand textareas

src/components/ExpandingTextarea/ExpandingTextarea.js

@@ -1,9 +1,36 @@
-/* eslint-disable react/prefer-stateless-function, no-console */
 import React, { Component } from 'react';
+import autosize from 'autosize';
 
 class ExpandingTextarea extends Component {
+  constructor(props) {
+    super(props);
+    this.textarea = null;
+  }
+  componentDidMount() {
+    // Delay the autosize initialisation so that the autosize can
+    // correctly calculate the height with the textarea value
+    window.setTimeout(
+      () => {
+        autosize(this.textarea);
+      },
+      100
+    );
+  }
+  componentDidUpdate() {
+    autosize.update(this.textarea);
+  }
+  componentWillUnmount() {
+    autosize.destroy(this.textarea);
+  }
   render() {
-    return <textarea {...this.props} />;
+    return (
+      <textarea
+        {...this.props}
+        ref={textarea => {
+          this.textarea = textarea;
+        }}
+      />
+    );
   }
 }