Documentation: Docker Swarm Deployment

Adding Documentation to docs/getting-started/index.mdx

I wrote instructions on how to Deploy OpenWebUI with Chroma, and Ollama to a Docker Swarm
I have tested on 3 seperate occasions to ensure everything works to the letter
Open in favor of https://github.com/open-webui/open-webui/pull/6389?notification_referrer_id=NT_kwDOATQEw7QxMzAzOTMyNjcwMDoyMDE4NjMwNw#issuecomment-2438532126

open-webui / docs