add 5.4 docker setup for CI

motivation: 5.4 is out! changes: use release docker images instead of nightly

Author: tomerd

docker/docker-compose.2004.54.yaml

@@ -0,0 +1,18 @@
+version: "3"
+
+services:
+
+ runtime-setup:
+ image: async-http-client:20.04-5.4
+ build:
+ args:
+ ubuntu_version: "focal"
+ swift_version: "5.4"
+
+ test:
+ image: async-http-client:20.04-5.4
+ environment: []
+ #- SANITIZER_ARG=--sanitize=thread
+
+ shell:
+ image: async-http-client:20.04-5.4