feat(Editor): use REST API endpoint to create step

packages/web/src/hooks/useCreateStep.js

@@ -0,0 +1,24 @@
+import { useMutation, useQueryClient } from '@tanstack/react-query';
+
+import api from 'helpers/api';
+
+export default function useCreateStep(flowId) {
+  const queryClient = useQueryClient();
+  const query = useMutation({
+    mutationFn: async ({ previousStepId }) => {
+      const { data } = await api.post(`/v1/flows/${flowId}/steps`, {
+        previousStepId,
+      });
+
+      return data;
+    },
+
+    onSuccess: () => {
+      queryClient.invalidateQueries({
+        queryKey: ['flows', flowId],
+      });
+    },
+  });
+
+  return query;
+}