docs(admin/workspace-proxies): add instructions to run using the Docker image (#7915)

* docs(admin/workspace-proxies): add instructions to run using the Docker image.

* make fmt

docs/admin/workspace-proxies.md

@@ -90,6 +90,32 @@ CODER_TLS_KEY_FILE="<key_file_location>"
 coder wsproxy server
 ```
 
+### Running in Docker
+
+Modify the default entrypoint to run a workspace proxy server instead of a regular Coder server.
+
+#### Docker Compose
+
+Change the provided [`docker-compose.yml`](https://github.com/coder/coder/blob/main/docker-compose.yaml) file to include a custom entrypoint:
+
+```diff
+  image: ghcr.io/coder/coder:${CODER_VERSION:-latest}
++ entrypoint: /opt/coder wsproxy server
+```
+
+#### Docker run
+
+```bash
+docker run --rm -it --entrypoint /opt/coder ghcr.io/coder/coder:latest wsproxy server
+```
+
+#### Custom Dockerfile
+
+```Dockerfile
+FROM ghcr.io/coder/coder:latest
+ENTRYPOINT ["/opt/coder", "wsproxy", "server"]
+```
+
 ### Selecting a proxy
 
 Users can navigate to their account settings to select a workspace proxy. Workspace proxy preferences are cached by the web browser. If a proxy goes offline, the session will fall back to the primary proxy. This could take up to 60 seconds.