Add step to add user to group

A user complained they could not access docker after installation.

Signed-off-by: Eric Curtin <eric.curtin@docker.com>

Author: ericcurtin

README.md

@@ -16,6 +16,7 @@ For Linux, install Docker Engine:
 
 ```bash
 curl -fsSL https://get.docker.com | sudo bash
+sudo usermod -aG docker $USER # to give user permission to access docker daemon
 ```
 
 Docker Model Runner is included in the above tools.