feat(node-parser): support async function (#1682)

.changeset/selfish-kids-own.md

packages/core/src/node-parser/base.ts

packages/core/src/node-parser/markdown.ts

packages/core/src/node-parser/sentence-window.ts

packages/core/src/utils/index.ts

packages/core/tests/node-parser/node-parser.test.ts

packages/llamaindex/src/indices/keyword/index.ts

packages/llamaindex/src/indices/summary/index.ts