docs: add LLM Instructions section and Next.js guide to documentation

[zaksnet]

Add copy-pastable instructions for an LLM to setup better auth with Convex and Nextjs. Every other method i have tried to achieve this has failed so far.

• Context7: It pulls the entire documentation, including migrations etc, and confuses the LLM.
• Direct URL: I think this one reads through the entire website, including migrations, tanstack guides etc and like context7 confuses the llm.

So far, this guide has worked for me in one shot with 2 of my projects.

Note: There are many ways this could be added to the docs, for example we could add a button at the begining of the documentation since this is what most users will look for these days. We could also extract the code blocks for the commands so that we dont have to update multiple files whenever there is an api change (I will create a sample PR for this).

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[erquhart]

Appreciate your work on this! Did you intentionally drop the llm guide from your commits here?

[zaksnet]

Appreciate your work on this! Did you intentionally drop the llm guide from your commits here?

Thanks @erquhart ! I'm not sure what you mean dropped the llm guide from my commits 🤔