devcontainer: enable accessing host Docker socket

.devcontainer/compose.yml

@@ -6,6 +6,7 @@ services:
       dockerfile: Dockerfile
     volumes:
       - ..:/workspace:cached
+      - /var/run/docker.sock:/var/run/docker-host.sock
     command: sleep infinity
   memcached:
     image: memcached:latest

.devcontainer/devcontainer.json

@@ -13,5 +13,8 @@
     "postCreateCommand": ".devcontainer/boot.sh",
     "forwardPorts": [
         4567
-    ]
+    ],
+    "features": {
+        "ghcr.io/devcontainers/features/docker-outside-of-docker:1": {}
+    }
 }