Add server-generated /config.js; add error boundary

web/src/components/ErrorBoundary.js

@@ -0,0 +1,32 @@
+import * as React from "react";
+
+class ErrorBoundary extends React.Component {
+    constructor(props) {
+        super(props);
+        this.state = { error: null, info: null };
+    }
+
+    componentDidCatch(error, info) {
+        this.setState({ error, info });
+        console.error("[ErrorBoundary] A horrible error occurred", info);
+    }
+
+    static getDerivedStateFromError(error) {
+        return { error: true, errorMessage: error.toString() }
+    }
+
+    render() {
+        if (this.state.info) {
+            return (
+                <div>
+                    <h2>Something went wrong.</h2>
+                    <pre>{this.state.error && this.state.error.toString()}</pre>
+                    <pre>{this.state.info.componentStack}</pre>
+                </div>
+            );
+        }
+        return this.props.children;
+    }
+}
+
+export default ErrorBoundary;