Add .devcontainer support (#342)

.devcontainer/Dockerfile

@@ -0,0 +1,10 @@
+# Which Ruby version to use. You may need to use a more restrictive version,
+# e.g. `3.0`
+ARG VARIANT=3.0
+
+# Pull Microsoft's ruby devcontainer base image
+FROM mcr.microsoft.com/devcontainers/ruby:${VARIANT}
+
+# Ensure we're running the latest bundler, as what ships with the Ruby image may
+# not be current, and bundler will auto-downgrade to match the Gemfile.lock
+RUN gem install bundler

.devcontainer/devcontainer.json

@@ -0,0 +1,29 @@
+{
+  "name": "Ruby",
+  "build": {
+    "dockerfile": "Dockerfile"
+  },
+
+  // Configure tool-specific properties.
+  "customizations": {
+    // Configure properties specific to VS Code.
+    "vscode": {
+      // Add the IDs of extensions you want installed when the container is created.
+      "extensions": [
+        "rebornix.Ruby"
+      ]
+    }
+  },
+
+  // Set the environment variables
+  // "runArgs": ["--env-file",".env"],
+
+  // Use 'forwardPorts' to make a list of ports inside the container available locally.
+  //   "forwardPorts": [],
+
+  // Use 'postCreateCommand' to run commands after the container is created.
+  "postCreateCommand": "bash .devcontainer/postcreate.sh",
+
+  // Set `remoteUser` to `root` to connect as root instead. More info: https://aka.ms/vscode-remote/containers/non-root.
+  "remoteUser": "vscode"
+}

.devcontainer/postcreate.sh

@@ -0,0 +1,4 @@
+#!/bin/bash
+
+bundle config set path vendor/bundle
+bundle install --jobs=1

.gitignore

@@ -10,6 +10,7 @@ doc
 
 # bundler
 .bundle
+vendor
 
 # jeweler generated
 pkg