add a devcontainer for codespace

Author: bjelline

.devcontainer/devcontainer.json

@@ -0,0 +1,16 @@
+{
+  "name": "Ruby 3.2 Dev Container",
+  "image": "mcr.microsoft.com/devcontainers/ruby:3.2",
+  "features": {
+    "ghcr.io/devcontainers/features/docker-in-docker:1": {}
+  },
+  "postCreateCommand": "bundle install",
+  "customizations": {
+    "vscode": {
+      "extensions": ["rebornix.Ruby"]
+    }
+  },
+  "mounts": [
+    "source=${localWorkspaceFolder},target=/workspace,type=bind,consistency=cached"
+  ]
+}