Update docker one liner to forward UID/GID

Closes #1425

Author: nhooyr

README.md

@@ -6,7 +6,7 @@ remote server, accessible through the browser.
 Try it out:
 
 ```bash
-docker run -it -p 127.0.0.1:8080:8080 -v "$PWD:/home/coder/project" codercom/code-server
+docker run -it -p 127.0.0.1:8080:8080 -v "$PWD:/home/coder/project" -u "$(id -u):$(id -g)" codercom/code-server:latest
 ```
 
 - **Code anywhere:** Code on your Chromebook, tablet, and laptop with a