Add codespace config (#54)

This sets up codespaces with Powershell support.

.devcontainer/devcontainer.json

@@ -0,0 +1,37 @@
+// For format details, see https://aka.ms/devcontainer.json. For config options, see the
+// README at: https://github.com/devcontainers/templates/tree/main/src/powershell
+{
+	"name": "PowerShell",
+	// Or use a Dockerfile or Docker Compose file. More info: https://containers.dev/guide/dockerfile
+	"image": "mcr.microsoft.com/powershell:lts-debian-11",
+	"features": {
+		"ghcr.io/devcontainers/features/common-utils:2": {},
+		"ghcr.io/devcontainers/features/docker-in-docker:2": {},
+		"ghcr.io/devcontainers/features/powershell:1": {},
+		"ghcr.io/devcontainers/features/dotnet:1": {}
+	},
+
+	"postCreateCommand": "sudo chsh vscode -s \"$(which pwsh)\" && ",
+
+	// Configure tool-specific properties.
+	"customizations": {
+		// Configure properties specific to VS Code.
+		"vscode": {
+			// Set *default* container specific settings.json values on container create.
+			"settings": { 
+				"terminal.integrated.defaultProfile.linux": "pwsh"
+			},
+			
+			// Add the IDs of extensions you want installed when the container is created.
+			"extensions": [
+				"ms-vscode.powershell"
+			]
+		}
+	}
+
+	// Use 'forwardPorts' to make a list of ports inside the container available locally.
+	// "forwardPorts": [],
+
+	// Uncomment to connect as root instead. More info: https://aka.ms/dev-containers-non-root.
+	// "remoteUser": "root"
+}