Add devcontainer configuration

devcontainers can be used by IDEs like VSCode to build the whole development environment in a container.
This allows you to keep dependencies, build, and all development aspects separated from any development.
It also allows contributors to instantly have a working, standardized development environment.
It also allows cloud development tools like GitHub Codespaces be automatically setup with the desired environment.

See https://containers.dev/ for more details

.devcontainer/setup.sh

@@ -0,0 +1,11 @@
+#!/usr/bin/env bash
+
+# Install Node packages
+pnpm install
+
+# Copy in skeleton configuration if there is no existing configuration
+if [ ! -d "config/" ]; then
+  echo "Adding skeleton config"
+  mkdir config/
+  cp -r src/skeleton/* config
+fi