Add devcontainer template for Crystal.

.devcontainer/Dockerfile

@@ -0,0 +1,17 @@
+FROM mcr.microsoft.com/devcontainers/base:ubuntu
+
+# Install packages
+# libpcre3-dev is needed if you wish to use ameba
+RUN apt-get update && apt-get install -y \
+    git \
+    build-essential \
+    curl \
+    libpcre3-dev \
+    && rm -rf /var/lib/apt/lists/*
+
+# Install Crystal
+RUN curl -fsSL https://crystal-lang.org/install.sh | bash
+
+# Switch to vscode user
+USER vscode
+WORKDIR /workspaces

.devcontainer/devcontainer.json

@@ -0,0 +1,13 @@
+{
+  "name": "Crystal Development",
+  "build": {
+    "dockerfile": "Dockerfile"
+  },
+  "remoteUser": "vscode",
+  "workspaceFolder": "/workspaces/PROJECT_NAME",
+  "customizations": {
+    "vscode": {
+      "extensions": ["crystal-lang-tools.crystal-lang"]
+    }
+  }
+}

shard.yml

@@ -0,0 +1,18 @@
+name: PROJECT_NAME
+version: 0.1.0
+
+authors:
+  - YOUR_NAME <YOUR_EMAIL>
+
+crystal: 1.0.0
+
+license: MIT
+
+development_dependencies:
+  ameba:
+    github: crystal-ameba/ameba
+    version: ~> 1.6.0
+
+targets:
+  PROJECT_NAME:
+    main: src/main.cr

spec/spec_helper.cr

@@ -0,0 +1 @@
+# spec_helper.cr

src/main.cr

@@ -0,0 +1 @@
+puts "Hello, PROJECT_NAME!"