add ci setup for 5.2 (#31)

motivation: 5.2 is coming soon, need to test against that target version

changes: add docker files setup for 5.2

docker/Dockerfile

@@ -1,6 +1,7 @@
 ARG swift_version=5.0
 ARG ubuntu_version=bionic
-FROM swift:$swift_version-$ubuntu_version
+ARG base_image=swift:$swift_version-$ubuntu_version
+FROM $base_image
 # needed to do again after FROM due to docker limitation
 ARG swift_version
 ARG ubuntu_version

docker/docker-compose.1804.52.yaml

@@ -0,0 +1,15 @@
+version: "3"
+
+services:
+
+  runtime-setup:
+    image: swift-aws-lambda:18.04-5.2
+    build:
+      args:
+        base_image: "swiftlang/swift:nightly-5.2-bionic"
+
+  test:
+    image: swift-aws-lambda:18.04-5.2
+
+  shell:
+    image: swift-aws-lambda:18.04-5.2