Grabbed dndbeyond's source code

```
~/go/bin/sourcemapper -output ddb -jsurl https://media.dndbeyond.com/character-app/static/js/main.90aa78c5.js
```

ddb_main/tools/js/smartComponents/Collapsible/CollapsibleHeading/CollapsibleHeading.tsx

@@ -0,0 +1,9 @@
+import * as React from "react";
+
+export default class CollapsibleHeading extends React.PureComponent<{}, {}> {
+  render() {
+    return (
+      <div className="ddbc-collapsible__heading">{this.props.children}</div>
+    );
+  }
+}