Config and docs update for deploying

[ric9176]

Firstly, thanks for putting this repo out, it's great 😀

This PR address a few small things I found when experimenting with it, particularly deploying.

1. The index name needs to be capitalized when using Weaviate otherwise it'll cause an error as the graphql schema that they use internally requires a capitalized name, if it's not given then it gets coerced, so if it's called langchain, in their generated schema that'd be Langchain and you'd get an error when querying. I've updated env examples and noted in the docs to avoid this.

2. There's an env var used for the prod url (VERCEL_URL) that needs to be updated, it also needs the NEXT_PUBLIC prefix to make it automatically available on the client, I've updated it to NEXT_PUBLIC_VERCEL_URL and added to the frontend .env.example

3. I haven't included this in the PR as I wasn't sure if the change is applicable for this repo. For the Vercel git hooks that enable auto deployment on merge to main to work correctly with turbo you'd need to update the turbo.json build outputs to: "outputs": ["**/dist/**", ".next/**", "!.next/cache/**"]. Then you could set deploymentEnabled to true in vercel.json or remove that file completely. Otherwise you run into a missing routes manifest issue with auto deploy.

Thanks again :-)