docs: add link checker and fix links (#1750)

apps/next/package.json

apps/next/scripts/validate-links.mts

...docs/llamaindex/getting_started/frameworks/cloudflare.mdx

...tent/docs/llamaindex/getting_started/frameworks/index.mdx

...ntent/docs/llamaindex/getting_started/frameworks/next.mdx

...ntent/docs/llamaindex/getting_started/frameworks/node.mdx

...ntent/docs/llamaindex/getting_started/frameworks/vite.mdx

...next/src/content/docs/llamaindex/migration/0.8-to-0.9.mdx

...tent/docs/llamaindex/migration/deprecated/agent/index.mdx

...xt/src/content/docs/llamaindex/modules/agent_workflow.mdx

apps/next/src/content/docs/llamaindex/modules/chat/rsc.mdx

...docs/llamaindex/modules/data_stores/chat_stores/index.mdx

.../docs/llamaindex/modules/data_stores/doc_stores/index.mdx

...ocs/llamaindex/modules/data_stores/index_stores/index.mdx

...t/docs/llamaindex/modules/data_stores/kv_stores/index.mdx

...cs/llamaindex/modules/data_stores/vector_stores/index.mdx

...ontent/docs/llamaindex/modules/evaluation/correctness.mdx

...ntent/docs/llamaindex/modules/evaluation/faithfulness.mdx

.../content/docs/llamaindex/modules/evaluation/relevancy.mdx

...llamaindex/modules/ingestion_pipeline/transformations.mdx