add devcontainer

.devcontainer/Dockerfile

@@ -0,0 +1,5 @@
+ARG VARIANT="3.4.2"
+FROM ghcr.io/rails/devcontainer/images/ruby:${VARIANT}
+
+RUN mkdir /run/kubernaut && \
+    chown vscode: /run/kubernaut

.devcontainer/boot.sh

@@ -0,0 +1,4 @@
+#!/bin/bash
+
+bundle update --bundler
+bundler install

.devcontainer/compose.yml

@@ -0,0 +1,11 @@
+---
+services:
+  kubernaut:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    volumes:
+      - ..:/workspace
+    command: sleep infinity
+  memcached:
+    image: memcached:latest

.devcontainer/devcontainer.json

@@ -0,0 +1,17 @@
+{
+    "dockerComposeFile": "compose.yml",
+    "service": "kubernaut",
+    "workspaceFolder": "/workspace",
+    "customizations": {
+        "vscode": {
+            "extensions": [
+                "Shopify.ruby-lsp",
+                "ms-azuretools.vscode-docker"
+            ]
+        }
+    },
+    "postCreateCommand": ".devcontainer/boot.sh",
+    "forwardPorts": [
+        4567
+    ]
+}