update devcontainer

Author: pycabbage

.devcontainer/devcontainer.json

@@ -8,7 +8,10 @@
 
   // Features to add to the dev container. More info: https://containers.dev/features.
 	"features": {
-		"ghcr.io/devcontainers/features/node:1": {}
+		"ghcr.io/devcontainers/features/node:1": {
+      "version": "21.6.1"
+    },
+		"ghcr.io/devcontainers/features/docker-outside-of-docker:1": {}
 	}
 
 	// Use 'forwardPorts' to make a list of ports inside the container available locally.