docker/README: add details regarding cool-seccomp-profile.json file

Signed-off-by: Méven Car <[email protected]>
Change-Id: If02b355a3b1b9cef46ce2014db03396ac1c27bc0

Author: meven

docker/README

@@ -60,6 +60,7 @@ On using the pre-made or self-built Docker images, see Collabora Online SDK:
 
 Runtime
 
-At runtime use the provided cool-seccomp-profile.json as seccomp profile (Ref: https://docs.docker.com/engine/security/seccomp/)
+At runtime use the provided `cool-seccomp-profile.json` as seccomp profile (Ref: https://docs.docker.com/engine/security/seccomp/)
+It improves security and performance, allowing the coolwsd process to better containerize documents processes:
 
    docker run --security-opt cool-seccomp-profile.json