Add DevContainers

Author: olivierlemasle

.devcontainer/devcontainer.json

@@ -0,0 +1,27 @@
+{
+  "name": "Jekyll",
+  "image": "mcr.microsoft.com/devcontainers/base:debian",
+  "containerEnv": {
+    "ENV LANG": "en_US.UTF-8",
+    "LANGUAGE": "en_US:en",
+    "TZ": "Etc/UTC",
+    "LANG": "en_US.UTF-8"
+  },
+  "features": {
+    "ghcr.io/devcontainers-contrib/features/ruby-asdf:0": {
+      // Cf Ruby version in https://pages.github.com/versions/
+      "version": "2.7.4"
+    }
+  },
+  "postCreateCommand": [
+    ".devcontainer/post-create.sh"
+  ],
+  "forwardPorts": [
+    // Jekyll server
+    4000,
+    // Live reload server
+    35729
+  ],
+  // Set `remoteUser` to `root` to connect as root instead. More info: https://aka.ms/vscode-remote/containers/non-root.
+  "remoteUser": "vscode"
+}

.devcontainer/post-create.sh

@@ -0,0 +1,14 @@
+#!/bin/sh
+
+# Install the version of Bundler.
+if [ -f Gemfile.lock ] && grep "BUNDLED WITH" Gemfile.lock >/dev/null; then
+    tail -n 2 Gemfile.lock | grep -C2 "BUNDLED WITH" | tail -n 1 | xargs gem install bundler -v
+fi
+
+# If there's a Gemfile, then run `bundle install`
+# It's assumed that the Gemfile will install Jekyll too
+if [ -f Gemfile ]; then
+    bundle install
+fi
+
+bundle exec jekyll --version

README.md

@@ -6,6 +6,14 @@
 
 This site uses Jekyll. You can find instructions for how to install and configure Jekyll on [https://jekyllrb.com/docs/](https://jekyllrb.com/docs/).
 
+You may also use a tool or service supporting [Development Containers](https://containers.dev/), such as Visual Studio Code or GitHub Codespaces. In that case, your development environment is already set up and includes Jekyll with the right version.
+
+Run Jekyll with:
+
+```bash
+bundle exec jekyll serve --livereload
+```
+
 ## How to Contribute
 You can contribute by:
 - writing an article,