Rename error boundary hook

It doesn't check whether it's actually used inside a GroupCallErrorBoundary, and it's generally useful for interacting with any error boundary, so I'm giving it a generic name to reflect this.

src/useErrorBoundary.ts

@@ -0,0 +1,29 @@
+/*
+Copyright 2023, 2024 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE in the repository root for full details.
+*/
+
+import { useMemo, useState } from "react";
+
+export type UseErrorBoundaryApi = {
+  showErrorBoundary: (error: Error) => void;
+};
+
+export function useErrorBoundary(): UseErrorBoundaryApi {
+  const [error, setError] = useState<Error | null>(null);
+
+  const memoized: UseErrorBoundaryApi = useMemo(
+    () => ({
+      showErrorBoundary: (error: Error) => setError(error),
+    }),
+    [],
+  );
+
+  if (error) {
+    throw error;
+  }
+
+  return memoized;
+}