docs(next): update homepage & init setup toturial (#1386)

...t/src/content/docs/llamaindex/starter/getting-started.mdx

apps/next/src/content/docs/llamaindex/starter/meta.json

apps/next/src/content/docs/llamaindex/starter/next.mdx

apps/next/src/content/docs/llamaindex/starter/node.mdx

apps/next/src/lib/const.ts

pnpm-lock.yaml