docs: fix typos, add API references (#1161)

apps/docs/docs/introduction.md

apps/docs/docs/modules/chat_engine.md

apps/docs/docs/modules/data_index.md

...s/modules/embeddings/available_embeddings/mixedbreadai.md

apps/docs/docs/modules/evaluation/index.md

apps/docs/docs/modules/ingestion_pipeline/transformations.md

apps/docs/docs/modules/llms/available_llms/deepseek.md

...ocs/modules/node_postprocessors/mixedbreadiai_reranker.md

apps/docs/docs/modules/query_engines/index.md

apps/docs/docs/modules/retriever.md

...aindex/src/storage/vectorStore/MongoDBAtlasVectorStore.ts