Add support for devcontainers.

.devcontainer/devcontainer.json

@@ -0,0 +1,27 @@
+// For format details, see https://aka.ms/devcontainer.json. For config options, see the
+// README at: https://github.com/devcontainers/templates/tree/main/src/debian
+{
+	"name": "QMK CLI",
+	// Or use a Dockerfile or Docker Compose file. More info: https://containers.dev/guide/dockerfile
+	"image": "ghcr.io/qmk/qmk_cli",
+	"customizations": {
+		"vscode": {
+			"extensions": [
+				"amodio.toggle-excluded-files"
+			]
+		}
+	},
+	"postCreateCommand": "git config --global --add safe.directory /workspaces/qmk_userspace && git submodule update --init --recursive && { [ -d /workspaces/qmk_userspace/qmk_firmware ] || git clone https://github.com/qmk/qmk_firmware.git /workspaces/qmk_userspace/qmk_firmware; } && git config --global --add safe.directory /workspaces/qmk_userspace/qmk_firmware && qmk config user.qmk_home=/workspaces/qmk_userspace/qmk_firmware && qmk config user.overlay_dir=/workspaces/qmk_userspace && qmk git-submodule"
+
+	// Features to add to the dev container. More info: https://containers.dev/features.
+	// "features": {},
+
+	// Use 'forwardPorts' to make a list of ports inside the container available locally.
+	// "forwardPorts": [],
+
+	// Configure tool-specific properties.
+	// "customizations": {},
+
+	// Uncomment to connect as root instead. More info: https://aka.ms/dev-containers-non-root.
+	// "remoteUser": "root"
+}