build(devcontainer): 🏗️ add devcontainer files

.devcontainer/devcontainer.json

@@ -0,0 +1,26 @@
+{
+  "name": "Rust",
+  "image": "mcr.microsoft.com/devcontainers/rust:1-1-bookworm",
+  "features": {
+    "ghcr.io/devcontainers-contrib/features/protoc:1": {
+      "version": "latest"
+    },
+    "ghcr.io/marcozac/devcontainer-features/buf:1": {
+      "installProtocGenBufBreaking": true,
+      "installProtocGenBufLint": true,
+      "version": "latest"
+    },
+    "ghcr.io/devcontainers-contrib/features/dprint-asdf:2": {
+      "version": "latest"
+    },
+    "ghcr.io/lee-orr/rusty-dev-containers/cargo-binstall:0": {}
+  },
+
+  "mounts": [
+    {
+      "source": "devcontainer-cargo-cache-${devcontainerId}",
+      "target": "/usr/local/cargo",
+      "type": "volume"
+    }
+  ]
+}

.github/dependabot.yml

@@ -0,0 +1,12 @@
+# To get started with Dependabot version updates, you'll need to specify which
+# package ecosystems to update and where the package manifests are located.
+# Please see the documentation for more information:
+# https://docs.github.com/github/administering-a-repository/configuration-options-for-dependency-updates
+# https://containers.dev/guide/dependabot
+
+version: 2
+updates:
+ - package-ecosystem: "devcontainers"
+   directory: "/"
+   schedule:
+     interval: weekly

.vscode/settings.json

@@ -3,6 +3,7 @@
     "actions",
     "config",
     "deps",
+    "devcontainer",
     "packaging",
     "rsjudge-grpc",
     "rsjudge-judger",