feat(github): include a devcontainer setup (#413)

.devcontainer/Dockerfile

@@ -0,0 +1,19 @@
+# syntax=docker/dockerfile:1
+FROM debian:bookworm-slim AS stainless
+
+RUN apt-get update && apt-get install -y \
+  nodejs \
+  npm \
+  yarnpkg \
+  && apt-get clean autoclean
+
+# Yarn
+RUN ln -sf /usr/bin/yarnpkg /usr/bin/yarn
+
+WORKDIR /workspace
+
+COPY package.json yarn.lock /workspace/
+
+RUN yarn install
+
+COPY . /workspace

.devcontainer/devcontainer.json

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+// For format details, see https://aka.ms/devcontainer.json. For config options, see the
+// README at: https://github.com/devcontainers/templates/tree/main/src/debian
+{
+  "name": "Debian",
+  "build": {
+    "dockerfile": "Dockerfile"
+  }
+
+  // Features to add to the dev container. More info: https://containers.dev/features.
+  // "features": {},
+
+  // Use 'forwardPorts' to make a list of ports inside the container available locally.
+  // "forwardPorts": [],
+
+  // Configure tool-specific properties.
+  // "customizations": {},
+
+  // Uncomment to connect as root instead. More info: https://aka.ms/dev-containers-non-root.
+  // "remoteUser": "root"
+}