docs(README.md): add new section links for vector stores

Author: willywg

README.md

@@ -39,7 +39,12 @@ Stream text with GPT-4, transcribe and translate audio with Whisper, or create i
     - [Embeddings](#embeddings)
     - [Batches](#batches)
     - [Files](#files)
+      - [For fine-tunning purposes](#for-fine-tunning-purposes)
+      - [For assistant purposes](#for-assistant-purposes)
     - [Finetunes](#finetunes)
+    - [Vector Stores](#vector-stores)
+    - [Vector Store Files](#vector-store-files)
+    - [Vector Store File Batches](#vector-store-file-batches)
     - [Assistants](#assistants)
     - [Threads and Messages](#threads-and-messages)
     - [Runs](#runs)