add codespace support

.devcontainer/devcontainer.json

@@ -0,0 +1,32 @@
+// For format details, see https://aka.ms/devcontainer.json. For config options, see the README at:
+// https://github.com/microsoft/vscode-dev-containers/tree/v0.162.0/containers/ubuntu
+{
+	"name": "Ubuntu",
+	"build": {
+		"dockerfile": "Dockerfile",
+		// Update 'VARIANT' to pick an Ubuntu version: focal, bionic
+		"args": { "VARIANT": "focal" }
+	},
+
+	// Set *default* container specific settings.json values on container create.
+	"settings": { 
+		"terminal.integrated.shell.linux": "/bin/bash"
+	},
+
+	// Add the IDs of extensions you want installed when the container is created.
+	"extensions": [
+        "platformio.platformio-ide",
+        "xaver.clang-format"
+		],
+
+	// Use 'forwardPorts' to make a list of ports inside the container available locally.
+	// "forwardPorts": [],
+
+	// Use 'postCreateCommand' to run commands after the container is created.
+	// "postCreateCommand": "uname -a",
+
+	// Comment out connect as root instead. More info: https://aka.ms/vscode-remote/containers/non-root.
+	"remoteUser": "vscode",
+
+	"postCreateCommand": "git submodule update --init"
+}