chore: bootstrap Docker development environment

.devcontainer/devcontainer.json

@@ -0,0 +1,13 @@
+{
+  "name": "vacationplanner2ics",
+  "dockerComposeFile": "../compose.yaml",
+  "service": "dev",
+  "workspaceFolder": "/workspace",
+  "shutdownAction": "stopCompose",
+  "customizations": {
+    "vscode": {
+      "extensions": ["rust-lang.rust-analyzer", "tamasfe.even-better-toml"]
+    }
+  },
+  "forwardPorts": [8080]
+}