[Multi-User Part 5]: Add a production Docker file and use a gunicorn configuration with it (#514)

- Add a productionized setup for the Khoj server using `gunicorn` with multiple workers for handling requests
- Add a new Dockerfile meant for production config at `ghcr.io/khoj-ai/khoj:prod`; the existing Docker config should remain the same

gunicorn-config.py

@@ -0,0 +1,10 @@
+import multiprocessing
+
+bind = "0.0.0.0:42110"
+workers = 4
+worker_class = "uvicorn.workers.UvicornWorker"
+timeout = 120
+keep_alive = 60
+accesslog = "access.log"
+errorlog = "error.log"
+loglevel = "debug"