Add Swift 5.8 CI and update nightly CI to Ubuntu 22.04 (#30)

Author: dnadoba

docker/docker-compose.2004.main.yaml

@@ -0,0 +1,22 @@
+version: "3"
+
+services:
+
+  runtime-setup:
+    image: swift-http-structured-headers:22.04-5.8
+    build:
+      args:
+        base_image: "swiftlang/swift:nightly-5.8-jammy"
+        ubuntu_version: "jammy"
+
+  unit-tests:
+    image: swift-http-structured-headers:22.04-5.8
+
+  test:
+    image: swift-http-structured-headers:22.04-5.8
+    environment:
+      - IMPORT_CHECK_ARG=--explicit-target-dependency-import-check error
+
+  shell:
+    image: swift-http-structured-headers:22.04-5.8
+

docker/docker-compose.2204.58.yaml

@@ -0,0 +1,22 @@
+version: "3"
+
+services:
+
+  runtime-setup:
+    image: swift-http-structured-headers:22.04-main
+    build:
+      args:
+        base_image: "swiftlang/swift:nightly-main-jammy"
+        ubuntu_version: "jammy"
+
+  unit-tests:
+    image: swift-http-structured-headers:22.04-main
+
+  test:
+    image: swift-http-structured-headers:22.04-main
+    environment:
+      - IMPORT_CHECK_ARG=--explicit-target-dependency-import-check error
+
+  shell:
+    image: swift-http-structured-headers:22.04-main
+