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/CollapsibleHeaderCallout/CollapsibleHeaderCallout.tsx

@@ -0,0 +1,26 @@
+import * as React from "react";
+
+interface Props {
+  extra: React.ReactNode;
+  value: React.ReactNode;
+}
+
+export default class CollapsibleHeaderCallout extends React.PureComponent<
+  Props,
+  {}
+> {
+  static defaultProps = {
+    extra: null,
+  };
+
+  render() {
+    const { extra, value } = this.props;
+
+    return (
+      <span className="ddbc-collapsible__header-callout">
+        <span className="ddbc-collapsible__header-callout-extra">{extra}</span>
+        <span className="ddbc-collapsible__header-callout-value">{value}</span>
+      </span>
+    );
+  }
+}