doc: Add cache volume mount to usage example

README.md

@@ -14,7 +14,7 @@ Install [Docker](https://docs.docker.com/engine/install/), then run:
 
 ```bash
 docker build -t didmar/whisper-api-server .
-docker run -d -p 127.0.0.1:8000:8000 didmar/whisper-api-server --workers 1
+docker run -d -p 127.0.0.1:8000:8000 -v .cache:/root/.cache:rw didmar/whisper-api-server --workers 1
 # Customize number of workers is needs to handle multiple requests in parallel
 ```