🐳 : Further Docker build Cleanup & Docs Update (#1502)

* refactor: post-cleanup changes:
- add more unnecessary paths to .dockerignore
- remove librechat.yaml from main compose file (prevents from being required)
- do not create librechat.yaml during build (does nothing)

* docs: make config file instructions easier to read, more info throughout other docs

* docs: add custom config to menu

* Update custom_config.md

* Update docker_compose_install.md

docker-compose.yml

@@ -25,7 +25,6 @@ services:
     volumes:
       - ./.env:/app/.env
       - ./images:/app/client/public/images
-      - ./librechat.yaml:/app/librechat.yaml
   mongodb:
     container_name: chat-mongodb
     image: mongo