Enhancement: Add note in Readme about Remix V2 routing convention.

[morrisonak]

I really like this SSE pattern you use in this Repo, I spun up a quick project withnpx create-remix@latest and built out the chat route. I went around in circles for longer than i care to admit on Error: No route matches URL "/chat/stream" When I finally changed routes/chat/stream.tsx to routes/chat.stream.tsx everything ran without issue. Same with chat._index.tsx

Thanks again for the live code session and this repo. It really unlocked the SSE with remix for me.

[moishinetzer]

No worries! Happy it helped 😄 feel free to open a PR and I'll get it merged