Co-authored-by: Alex Yang <himself65@outlook.com>

Allows our scripts to be run repeatedly with vector store backing and
persistence without throwing an error.

This is rudimentary support which doesn't work if the document has
changed over time.

Also added the insert and delete functions so that documents can be
added manually.

Makes it easier to get started although now they have to use npm instead
of pnpm

Putting in a max tokens into the request was a mistake.